-4x + 3y = 9
-12x - 7y = -4
I think you should use the addition method. In the substitution method, you have to solve for one of the variables, then plug it into ...
The solution consists of:
(1) brief explanations of how to do the substitution method and the addition method
(2) which method is easier in this case
(3) how to use that method to find the solution to this system of equations.