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## Algebra (all content)

### Course: Algebra (all content)>Unit 2

Lesson 12: Old school equations with Sal

# Linear equations 2

solving equations of the form AX+B=C. Created by Sal Khan.

## Want to join the conversation?

• how do you do 7x-4=24
• When you have your equation 7x-4 = 24, you can take the number to left side and place it in the right. However, you need to change the operation

7x-4 = 24
7x=24+4
7x=28.

Now, you need to divide each side by the coefficient (if there is). The coefficient here is 7, so you nee to divide each side by 7

7x=28
7x/7=28/7
x=4.

That is how you solve a linear equation. I hope this helps!
• I am lost how he got ten minus nine over twelve
• In order to subtract 3/4 from 5/6 he needs to find a common denominator for the two fractions. (Preferably the smallest possible.) The smallest number that is a multiple of both 4 and 6 is 12. Make two equivalent fractions by multiplying each fraction by the number that gives 12 in the denominator. For 5/6 it's 2, and for 3/4 it'3. This gives 10/12 - 9/12. Whatever the numerator turns out to be the denominator in the answer will be 12, so Sal can write 10-9/12.
• do we have to follow all those steps is their a shorter and/or faster way to do it
• how does Sal check his work at
• You should always get in the habit of checking your work. If you can find and fix errors, you get better grades.
• I am a bit confused I can't figure out how to take away both sides if that makes sense how you have to do the same to both sides
thank you if you can help!
• It's okay... Everybody learns!
Say we have this equation...
9(4x-7) + 19 = 12x
we can use the distributive property to multiply:
36x - 63 + 19 = 12x
Let's simplify and clean things up:
36x - 44 = 12x
Now for your question... We want to make the 12x scooch onto the left hand side, and when doing so, we want the constant on the right. 36x stays right where it is. Essentially, what Mr. Sal was doing was (in this example) is he subtracted 12x from both sides and left it as
36x - 44 - 12x = 0
because 0 fills all the random spaces (0's just nice like that).
Now we can move -44 to its rightful place and fill that annoying gap.
36x - 12x = 44
Simplify to clean it up:
24x = 44
x = 44/24
x = 1 5/6
Hope this helped cgr6507!
-Ella :)
• how do you do 5x=5
2