3x-5=15-x

+x +x

Begin by combining your like terms (x) by adding x to each side

4x - 5 = 15

** +5 +5**

Add 5 to both sides in order to combine constants

4x = 20

/4 /4

Divide by 4 to isolate the variable

x = 5

3x-5=15-x

Okay, when you are working an algebra equation, or an equation with variables in it, the first thing you want to do is get all "like" variables on the same side.

3x-5=15-x --> add x to both sides. (3x+x=4x; x+-x=1)

Rewrite the problem:

3x+x-5=15 ---> add like things together (3x+x=4x)

4x-5=15 ------> now add 5 to both sides (-5+5=1; 5+15=20)

Rewrite your problem:

4x=15+5 ----> add like things together! (15+5=20)

4x=20 -----> now in order to get x by itself divide both sides by 4.

4x/4=20/4 -----> 4x/4=x; 20/4=5

Rewrite the problem to get your answer!!!!

x=5!

Hope this helps!!! :)