2x -2y = 12--------------(1)
8x - 11y = 78 -----------(2)
4 * (1);
8x - 8y = 48 -------------(3)
(2) - (3);
you will get,
- 3y = 30
y = - 10;
substitute y = - 10 in (1), you wil get
2x - 2*(-10 ) = 12
2x +20 = 12
2x = 12 - 20
2x = - 8
x = -8/2
x = -4;
therefore x = -4; y = -10