Is there anyone on Khan Academy anymore? All these comments are from years ago. I see no active or recent questions. If I ask a question will it even get answered?

There are plenty of people on Khan Academy. Sometimes users ask questions more often than other times.

where does the subtracting 18 come from?

To get x on one side of the equation so Sam subtracted 18 from each side because what you do to one side, you have to do to the other

If JK+KL=114 (1:28) does that mean KL+JK also equals 114?

Yes, because it doesn't matter which order things are added together in. (commutatative property of addition)

Main content

Algebra basics

Course: Algebra basics > Unit 8

Lesson 1: Equations & geometry

Equation practice with segment addition

Name: Equation practice with segment addition
Uploaded: 2013-07-11T18:09:20Z
Description: If we split a line segment into two segments, the length of the total segment equals the sums of the lengths of the two smaller segments. We can make an equation out of the given information. After we solve for the value of x, we can substitute that value back into the expression for the length we are seeking.

Google Classroom

If we split a line segment into two segments, the length of the total segment equals the sums of the lengths of the two smaller segments. We can make an equation out of the given information. After we solve for the value of x, we can substitute that value back into the expression for the length we are seeking. Created by Sal Khan.

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sandi thigpin
Posted 3 years ago. Direct link to sandi thigpin's post “the captions said jfk lma...”
the captions said jfk lmao
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sophia kim
Posted 2 years ago. Direct link to sophia kim's post “Khan academy saved me”
Khan academy saved me
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- Kenneth Morillo
  Posted a year ago. Direct link to Kenneth Morillo's post “I agree with that.”
  I agree with that.
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4806001719
Posted a year ago. Direct link to 4806001719's post “I like o know if monkes e...”
I like o know if monkes eat more than bannanas
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(4 votes)
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(っ◔◡◔)っ ♥ Menou ♥
Posted a year ago. Direct link to (っ◔◡◔)っ ♥ Menou ♥'s post “Wait, if I have a perpend...”
Wait, if I have a perpendicular set of lines and I needed to use this method to figure it out, how would I do that? I don't even know what it's called because I was late to starting school and I need help DX
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(4 votes)
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- Luke
  Posted 9 months ago. Direct link to Luke's post “If you have two lines tha...”
  If you have two lines that are perpendicular, it means that they intersect each other at a 90-degree angle. One way to determine if two lines are perpendicular is by checking the slopes of the lines.
  
  If the slopes of two lines are negative reciprocals of each other, then they are perpendicular. The negative reciprocal of a slope is found by flipping the fraction upside down and changing its sign. For example, the negative reciprocal of 2/3 is -3/2.
  
  To use this method to determine if two lines are perpendicular, you need to find the slopes of the two lines, and then check if they are negative reciprocals of each other. If they are, then the lines are perpendicular.
  
  For example, if you have two lines with slopes of 2 and -1/2, you can determine if they are perpendicular by finding the negative reciprocal of each slope.
  
  The negative reciprocal of 2 is -1/2
  The negative reciprocal of -1/2 is 2
  Since the slopes of the two lines are negative reciprocals of each other, the lines are perpendicular.
  Comment on Luke's post “If you have two lines tha...”
  (1 vote)
Michael
Posted 7 years ago. Direct link to Michael's post “Is there anyone on Khan A...”
Is there anyone on Khan Academy anymore? All these comments are from years ago. I see no active or recent questions. If I ask a question will it even get answered?
Button navigates to signup pageComment on Michael's post “Is there anyone on Khan A...”
(3 votes)
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- trek
  Posted 7 years ago. Direct link to trek's post “There are plenty of peopl...”
  There are plenty of people on Khan Academy. Sometimes users ask questions more often than other times.
  Comment on trek's post “There are plenty of peopl...”
  (3 votes)
Esteban Montoya
Posted 3 years ago. Direct link to Esteban Montoya's post “where does the subtractin...”
where does the subtracting 18 come from?
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(2 votes)
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- Ashlee Lewis
  Posted 3 years ago. Direct link to Ashlee Lewis's post “To get x on one side of t...”
  To get x on one side of the equation so Sam subtracted 18 from each side because what you do to one side, you have to do to the other
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  (2 votes)
DB1440955
Posted 8 years ago. Direct link to DB1440955's post “If JK+KL=114 (1:28) does ...”
If JK+KL=114 (
1:28
) does that mean KL+JK also equals 114?
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(2 votes)
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- sage.liem.9
  Posted 8 years ago. Direct link to sage.liem.9's post “Yes, because it doesn't m...”
  Yes, because it doesn't matter which order things are added together in. (commutatative property of addition)
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  (2 votes)
Jalil Howard
Posted 6 years ago. Direct link to Jalil Howard's post “this is a little confusin...”
this is a little confusing sometimes and I need help
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(2 votes)
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- 💲⚔💎💝Max Lennon💝💎⚔💲
  Posted a year ago. Direct link to 💲⚔💎💝Max Lennon💝💎⚔💲's post “what do you need help wit...”
  what do you need help with
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  (1 vote)
guyawesome356
Posted 8 years ago. Direct link to guyawesome356's post “Why is y used as secondar...”
Why is y used as secondary (as in x + y = 2x)
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klickerklown
Posted 8 years ago. Direct link to klickerklown's post “So how do you know which ...”
So how do you know which one to use at the right time? (like subtraction,addition,division, and multiplication.)
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Video transcript

So we have this line segment JL here, and we have point K that also sits on that segment. And they tell us that JK is equal to 7x plus 9. So this distance right over here is equal to 7x plus 9. Then they tell us that JL is equal to 114. So JL is the entire length of the segment. So this entire thing is equal to 114. Then they tells us that KL is equal to 9x plus 9. So this right over here is equal to 9x plus 9. And they say find KL. So they essentially want us to figure out what does 9x plus 9 equal? And to figure that out, we have to figure out what x equals. And lucky for us, they've given us all the information we need. They tell us that the entire segment is 114 long. And they don't give us any units. It's just 114. It has a length of 114. And we know that this segment, JK plus KL, added together, is going to be equal to the length of the entire thing. So we could say that 7x plus 9-- actually let me write it this way. We could write that JK, so the length of segment JK plus the length of segment KL is going to be equal to 114. And we know that the length of segment JFK is 7x plus 9. We know that the length of segment KL is 9x plus 9. And this is going to be equal to 114. And now we just have to break out a little bit of our algebraic skills. So the first thing we might want to do is, let's see, we have two terms that have x's in them. If I have 7 x's, and I were to add that to another 9 x's, that means I'm going to have 16 x's. And then if I have-- so this is just plain old 9, and I add it to another 9. That's going to give me 18. And that's going to be equal to 114. Now I just subtract 18 from both sides. Let me do that explicitly. So I subtract 18 from both sides. On the left-hand side I have 16 x, and on the right-hand side, I'm going to have 114 minus 18. Well, if I were to subtract 14, that would get me to 100. And I'm going to subtract 4 more than that, so that's going to get me to 96. And now we just divide both sides by 16. And let's see, this looks like 96 divided by 16-- we could do it explicitly, but it looks like it's going to be 6. 6 times 10 is 60. 6 times 6 is 36. 60 plus 36 is 96. So we get x is equal to 6. Now we're not done yet. We're not looking just for x. We're looking for the length of KL. KL is 9x plus 9. Let me write that down. So KL is equal to 9x plus 9. They told us that right over there, is equal to 9x plus 9. We just figured out that x is equal to 6. So this is equal to 9 times 6 plus 9. And this is equal to-- 9 times 6 is 54, plus 9, is equal to 63. So KL is equal to 63.