kerjakan dengan campuran ×+3y=-3, 2×-y=15

= x + 3y = -3 (x2)
   2x - y = 15

= 2x + 6y = -6
   2x - y = 15
____________-
7y = 21
y = 3

x + 3(3) = -3
x + 9 = -3
x = -12