To get the answer, you have to isolate x. The first step to do so is to get the x's together, and the rest on the other side. You add 2 to both sides to get rid of the -2 on the left side, and add x to both sides to get rid of the -x on the right side so you have:
6x=-18
Your final step to isolating x is to divide both sides by 6 so you get:
x=-3