Alright! So the first step to solving 3x-3=-18 is isolating the variable. In other words, you want to make sure x is all by itself on one side of the equal sign.
3x-3=-18
+3 +3 Remember: What you do to one side, you have to do to the other.
3x = -15
Now divide by the coefficient (the number in front of x).
(3x)/3 = (-15)/3
x = -5
