What's the answer to:

‎X + 9 = 18 - 2x?

Remember you can do anything to an equation as long as you do it to both sides

x+9=18-2x

add 2x to both sides

2x+x+9=18+2x-2x

3x+9=18+0

3x+9=18

minus 9 both sides

3x+9-9=18-9

3x+0=9

3x=9

divide both sides by 3

(3x) / 3=9/3

(3/3) x=3

1x=3

x=3