Answer :
Ok so you have your two equations:
(1) 2x + 3y = -11 (I am assuming you meant 2x + 3y instead of 2x + 3x at least?)
(2) x - y = 12
x = y + 12
If we substitute equation (2) into equation (1) we get:
2(y + 12) + 3y = -11
2y + 24 + 3y = -11
5y = -35, therefor y = -7
If y = -7, from equation (2) we get:
x = -7 + 12 = 5