Question

How can you solve an equation with a variable on both sides

Answer 1

It depends. You'd need to give some example, but generally the idea is to put all variables on one side and everything else on the other side.

$15 +2x =2+5x\\ 2x-5x=2-15\\ -3x=-13\\ x=\dfrac{13}{3}$

Answer 2

It depends on where you have it for example, p=3, m=2
 8p+5=7m+15
24+5=14=15
29=29