x - 3y = -11
-x + 2y = 7
We minus these equations : x - 3y - (-x + 2y) = -18
= x - 3y + x - 2y = -18
2x - 5y = -18
Now, we add these equations :
x - 3y = -11
-x + 2y = 7
-> x - 3y - x + 2y = -4
-y = -4
y = 4
Replace it in 2x - 5y = -18
2x - 20 = -18
2x = -18 + 20 = 2
x = 1
Recheck : 1 - 3 x 4 = -11
-1 + 8 = 7.
