what is the value of x?
3 - x = 12
You can move -x to the right side of the = and 12 to the left side of the equal. After you do that, this becomes.
Notice when you move, this changes the + or - sign.
so x = -9
Ok, we need to isolate x and there are two ways to do this. First, subtract 3 from both sides.
-3 + 3 - x = 12 - 3.
The two 3's on the left cancel and we have
-x = 9
Now, we multiply both sides by -1 so that x is by itself and we have x = -9!