-10x - 3y = -18
-7x - 8y = 11

1. Multiply the top equation by 7 (where did I get the 7?)
2. Multiply the bottom equation by 10 (where did I get the 10?)
3. Add the equations together. Add the left sides and the right sides separately.
4. Solve the resulting equation for y.
5. Take the value for y and insert it into either of the equations and solve for x.

viola!