Покрокове пояснення:

2b + (7a - 9b) = 2b + 7a - 9b = 7a - 7b = 7(a - b)

-4x - (8p - 4x) = -4x - 8p + 4x = -8p

(5 + a) + (7a - 5) = 5 + a + 7a - 5 = 13a - 5

(4 - 8b) + (-8b - 15) = 4 - 8b - 8b - 15 = -16b - 11