Well, all we have to do is make the s be on one side of the equation BY ITSELF, so we take our original problem:

First, we add 8 to both sides of the equation:

Notice what's left on the right side:

Now we divide both sides of the equation by 2:

Look what's left:

And problem solved.

All you have to do is move everything to the other side by doing the opposite to both sides of the equation.