Question

What value of x makes this sentence true?

5x + 12 = x – 8

Answer 1

Move x to one side and 12 to the other side

5x - x = ?

-8 - 12 = ?

Answer 2

Remember you can do what Mehek says by doing the same thing to both sides of the equation
5x+12=x-8
5x+12-12 = x-8-12 (subtract 12 from both sides
5x+0=x-20
5x-x=x-x-20 (substract x from both sides)
4x=-20
4x/4=-20/4 (divide both sides by 4)
x=-5

checking we have
5(-5)+12=(-5)-8
-25+12=-13
-13=-13 it checks out