Use the subtraction method.
2 (x - 2y = 15) multiply top equation by 2 so we can subtract
2x - 4y = 30
2x + 4y = -18 (subtracted, we get 4x = 12...divide by 4...x = 3)
place the value for X into an original equation and solve for Y.
2(3) + 4y = -18
6 + 4y = -18
-6 -6
4y = -24 (divide by 4)
y = -6 Solution......(3, -6)