First row
∴ x = -9
∴ (1/3)x + y = 12
(1/3)(-9) + y = 12
-3 + y = 12
∴ y = 15
Second row
∴ x = -3
∴(1/3)x + y = 12
(1/3)(-3) + y = 12
-1 + y = 12
∴ y = 13
Third row
∴ x = 0
∴(1/3)x + y = 12
(1/3)(0) + y = 12
0 + y = 12
∴ y = 12
Fourth row
∴ x = 3
∴(1/3)x + y = 12
(1/3)(3) + y = 12
1 + y = 12
∴ y = 11
Fifth row
∴ x = 9
∴(1/3)x + y = 12
(1/3)(9) + y = 12
3 + y = 12
∴ y = 9
