When you solve the equation x plus nine equals fifteen, how do you know what number to subtract from both sides? Why is it important to subtract the same number from both sides of the equation?

Question

taylor<3srin · Answer

So when you solve for X what do you know needs to be done in order to solve?

anonymous · Answer

you need to know what plus 9=15

taylor<3srin · Answer

Yes that is correct, but I was looking for what needs to be done  in order to get that. Why do you subtract numbers from both sides?

taylor<3srin · Answer

There is one variable you need to solve for, x. To solve for it, you need to subtract 9 from 15 in order for it to be all alone on the left side.

taylor<3srin · Answer

$$(x+9)-9=(15)-9$$

Using cancellation, the 9 on the left side of the equation is now gone poof! Leaving just the X alone.

$$X=6$$

anonymous · Answer

I see so First you need to subtract from both sides.

taylor<3srin · Answer

Yes you subtract from both sides to get the variable you are solving for alone!

anonymous · Answer

Thanks Taylor

taylor<3srin · Answer

Mhmm

anonymous · Answer

That helped alot

taylor<3srin · Answer

I'm glad.