8x + 3 = 5x - 18
First, we'll want to move the x's on to the same side, and the numbers on to the same side.
Let's move 5x over to the left.
Subtract 5x from both sides.
8x - 5x + 3 = 5x - 5x - 18
3x + 3 = -18
Now, let's move 3 to the right.
Subtract 3 from both sides.
3x + 3 - 3 = -18 - 3
3x = -21
Divide both sides by three
3x/3 = -21/3
x = -7