8x + 4y = -20 ⇒ 24x + 12y = -60
6x + 6y = -18 ⇒ 12x + 12y = -36
12x = -24
12 12
x = -2
8x + 4y = -20
8(-2) + 4y = -20
-16 + 4y = -20
+ 16 + 16
4y = -4
4 4
y = -1
(x, y) = (-2, -1)
-7x + 7y = -21 ⇒ -14x + 14y = -42
4x - 2y = 22 ⇒ 28x - 14y = 154
14x = 112
14 14
x = 8
-7x + 7y = -21
-7(8) + 7y = -21
-56 + 7y = -21
+ 56 + 56
7y = 35
7 7
y = 5
(x, y) = (8, 5)