how do i solve if 8 is 90% of n

Change 90% into a decimal: 0.90 or 0.9 Translate the key words: "of" = multiply and "is" means "=" Translate the phrase: "8 is 90% of n" becomes 8 = 0.90n Solve for "n" by dividing both sides by 0.9 Alternatively, set up a proportion: 8/n = 90/100 Cross multiply and divide to solve for "n" Hope this helps.

At 0:41, is 5. (1) not the same as 5 x x 1 ?

If another operation is before the parentheses, then you don't multiply. If you have something like 3- (-3), you just subtract the -3. If yo have 4*(5), you only multiply once.

Why is X the most used variable is it because of the x and y axis or some other reason

yes, it is! x and y are commonly used as variables on khan, but what they are most famous for is the the x and y axis, but as sal says "You can use any variable but were going to use x and y" they just use it on khan for equations and other math problems often! btw off topic, im a fellow programmer two! nice to meet you!:D

Does the letter stand for something in each problem?

Yes, it stands for the variable’s value.

Why do we use a variable. What is its purpose?

A variable is used to define an unknown letter and it can be any number. However, as you work towards more advanced math, certain letters represent certain values, such as the letter e, which is Euler's number. I hope this helped!

How do you do 2(x-7)=4(x-4)

1) Distribute 2 and 4 to eliminate the parentheses: `2x - 14 = 4x - 16` 2) Subtract one of the X terms from both sides. You can pick either one. Let's say you subtract 2x from both sides (this may be a little easier to work with a positive value as a result). `- 14 = 2x - 16` 3) To isolate the remaining X term, you need to add 16 to both sides: `2 = 2x` 4) Then, complete the problem by dividing both sides by 2. `1 = x` Hope this helps.

So is evaluating expressions is like you have a variable that stands for a number so you figure out what the value of the variable is first isolate the variable then do the inverse operation?

Yes, because if you want to isolate the variable in 3+X=7, you could do 3-3+X=7-3, and the 3 and 3 cancel out.

I have 2 questions: 1. Are variables called variables because they can vary from time to time? 2. ANYONE TELL ME, WHAT IN THE WORLD IS A *QUEESTIIIIION*!?

1. Yes, I believe so. 2. (from dictionary) a sentence worded or expressed so as to elicit information.

Main content

6th grade (Illustrative Mathematics)

Course: 6th grade (Illustrative Mathematics) > Unit 6

Lesson 7: Lesson 6: Write expressions where letters stand for numbers

Evaluating an expression with one variable

Name: Evaluating an expression with one variable
Uploaded: 2011-02-20T16:40:17Z
Description: Learn how to evaluate an expression with variables using a technique called substitution (or "plugging in").

CCSS.Math:

6.EE.A.2

6.EE.A.2c

Google Classroom

Learn how to evaluate an expression with variables using a technique called substitution (or "plugging in"). Created by Sal Khan and Monterey Institute for Technology and Education.

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Zane( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)
Posted 3 years ago. Direct link to Zane( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)( ͡° ͜ʖ ͡°)'s post “how do i solve if 8 is 90...”
how do i solve if 8 is 90% of n
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(10 votes)
Answer
- Kim Seidel
  Posted 3 years ago. Direct link to Kim Seidel's post “Change 90% into a decimal...”
  Change 90% into a decimal: 0.90 or 0.9
  Translate the key words: "of" = multiply and "is" means "="
  Translate the phrase: "8 is 90% of n" becomes 8 = 0.90n
  Solve for "n" by dividing both sides by 0.9
  
  Alternatively, set up a proportion:
  8/n = 90/100
  Cross multiply and divide to solve for "n"
  
  Hope this helps.
  Comment on Kim Seidel's post “Change 90% into a decimal...”
  (13 votes)
Darren
Posted 9 years ago. Direct link to Darren's post “At 0:41, is 5. (1) not th...”
At
0:41
, is 5. (1) not the same as 5 x x 1 ?
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(5 votes)
Answer
- N Peterson
  Posted 9 years ago. Direct link to N Peterson's post “If another operation is b...”
  If another operation is before the parentheses, then you don't multiply. If you have something like 3- (-3), you just subtract the -3.
  If yo have 4*(5), you only multiply once.
  Comment on N Peterson's post “If another operation is b...”
  (7 votes)
Suhani
Posted 3 years ago. Direct link to Suhani's post “Why is X the most used va...”
Why is X the most used variable is it because of the x and y axis or some other reason
Button navigates to signup pageComment on Suhani's post “Why is X the most used va...”
(4 votes)
Answer
- 𝘽𝘼𝙏𝙈𝘼𝙉
  Posted 3 years ago. Direct link to 𝘽𝘼𝙏𝙈𝘼𝙉's post “yes, it is! x and y are c...”
  yes, it is! x and y are commonly used as variables on khan, but what they are most famous for is the the x and y axis, but as sal says "You can use any variable but were going to use x and y" they just use it on khan for equations and other math problems often! btw off topic, im a fellow programmer two! nice to meet you!:D
  Comment on 𝘽𝘼𝙏𝙈𝘼𝙉's post “yes, it is! x and y are c...”
  (6 votes)
Tucker Christiansen
Posted 3 years ago. Direct link to Tucker Christiansen's post “If t=11, what is the answ...”
If t=11, what is the answer?
Button navigates to signup pageComment on Tucker Christiansen's post “If t=11, what is the answ...”
(3 votes)
Answer
- Ridhi superr34
  Posted a month ago. Direct link to Ridhi superr34's post “expression: 5t+3 If t=11...”
  expression: 5t+3
  
  If t=11:
  
  (5x11)+3
  =55+3
  =58
  
  Hope this helps!
  Button navigates to signup page
  (1 vote)
luke.shultz
Posted 2 months ago. Direct link to luke.shultz's post “why does it look like he ...”
why does it look like he is about to hack the main frame
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(4 votes)
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- korbin
  Posted 9 days ago. Direct link to korbin's post “frfrfr”
  frfrfr
  Comment on korbin's post “frfrfr”
  (1 vote)
28mkraabe
Posted 5 months ago. Direct link to 28mkraabe's post “Does the letter stand for...”
Does the letter stand for something in each problem?
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(3 votes)
Answer
- WisteriaGrove
  Posted 2 months ago. Direct link to WisteriaGrove's post “Yes, it stands for the va...”
  Yes, it stands for the variable’s value.
  Button navigates to signup page
  (2 votes)
Jia Ali
Posted 3 years ago. Direct link to Jia Ali's post “Why do we use a variable....”
Why do we use a variable. What is its purpose?
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(2 votes)
Answer
- Victor
  Posted 3 years ago. Direct link to Victor's post “A variable is used to def...”
  A variable is used to define an unknown letter and it can be any number. However, as you work towards more advanced math, certain letters represent certain values, such as the letter e, which is Euler's number. I hope this helped!
  Comment on Victor's post “A variable is used to def...”
  (4 votes)
a3for1
Posted 5 years ago. Direct link to a3for1's post “I have 2 questions: 1. Ar...”
I have 2 questions:
1. Are variables called variables because they can vary from time to time?
2. ANYONE TELL ME, WHAT IN THE WORLD IS A QUEESTIIIIION!?
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(1 vote)
Answer
- Lin Gh.
  Posted 5 years ago. Direct link to Lin Gh.'s post “1. Yes, I believe so. 2. ...”
  1. Yes, I believe so.
  2. (from dictionary) a sentence worded or expressed so as to elicit information.
  Button navigates to signup page
  (5 votes)
Debra Overman
Posted 6 years ago. Direct link to Debra Overman's post “How do you do 2(x-7)=4(x-...”
How do you do 2(x-7)=4(x-4)
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(2 votes)
Answer
- Kim Seidel
  Posted 6 years ago. Direct link to Kim Seidel's post “1) Distribute 2 and 4 to...”
  1) Distribute 2 and 4 to eliminate the parentheses: 2x - 14 = 4x - 16
  2) Subtract one of the X terms from both sides. You can pick either one. Let's say you subtract 2x from both sides (this may be a little easier to work with a positive value as a result).
  - 14 = 2x - 16
  3) To isolate the remaining X term, you need to add 16 to both sides: 2 = 2x
  4) Then, complete the problem by dividing both sides by 2. 1 = x
  
  Hope this helps.
  Button navigates to signup page
  (3 votes)
cole.bethany
Posted 10 years ago. Direct link to cole.bethany's post “So is evaluating expressi...”
So is evaluating expressions is like you have a variable that stands for a number so you figure out what the value of the variable is first isolate the variable then do the inverse operation?
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(2 votes)
Answer
- Fred Xu
  Posted 4 years ago. Direct link to Fred Xu's post “Yes, because if you want ...”
  Yes, because if you want to isolate the variable in 3+X=7, you could do 3-3+X=7-3, and the 3 and 3 cancel out.
  Button navigates to signup page
  (2 votes)

Video transcript

A local hospital is holding a raffle as a fundraiser. The individual cost of participating in the raffle is given by the following expression-- 5t plus 3, or 5 times t plus 3, where t represents the number of tickets someone purchases. Evaluate the expression when t is equal to 1, t is equal to 8, and t is equal to 10. So let's first take the situation where t is equal to 1. Then this expression right over here becomes-- and I'll use that same color-- becomes 5 times 1. 5 times 1 plus 3. 5 times 1 plus 3, and we know from order of operations, you do the multiplication before you do the addition. So this will be 5 times 1 is 5 plus 3, and then this is clearly equal to 8. Now let's do it when t is equal to 8. So when t is equal to 8, this expression becomes-- and I'll do the same colors again-- 5 times 8 plus 3. Same color of green. And once again, 5 times 8 is 40, and then we have the plus 3, there so this is equal to 43. And so we have the last situation, with t is equal to 10. I'll do that in blue. So we have 5 times 10. So 5t is 5 times 10. Instead of a t, put a 10 there. 5 times 10 plus 3. That's a slightly different shade of green, but I think you get the idea. 5 times 10 is 50. We do 50, and then we're going to have to add 3 to that, and that is equal to 53. And we're done.

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