15x - x - 4x + 7x = (15 - 1 - 4 + 7)x = 17x
6b + b - 2 - b - b + 11 = (6 - 1 - 1 + 0)b + 11 = 4b + 11
16ax + x - ax - x = (16 - 1 - 1 + 0)ax = 14ax
12ay - ay - ay + 6a - 7a = (12 - 1 - 1 + 6 - 7)ay = 9ay - a
15x - x - 4x + 7x = (15 - 1 - 4 + 7)x = 17x
6b + b - 2 - b - b + 11 = (6 - 1 - 1 + 0)b + 11 = 4b + 11
16ax + x - ax - x = (16 - 1 - 1 + 0)ax = 14ax
12ay - ay - ay + 6a - 7a = (12 - 1 - 1 + 6 - 7)ay = 9ay - a