Question

-18x+9y=72 how do I solve that

Answer 1

This depend on what you are solving for. But lets do this:
Divide the WHOLE equation by 9. By doing this, you simplify the equation and get y by itself. Now you have -2x+y=8. Isolate y. Do this by adding 2x to each side of the equals sign. you now have y=2x + 8.