-2,8a * (-5b) = 14ab
-12a - 25b + 18a + 14b = (-12a + 18a) + (-25b + 14b) = 6a - 11b
b - (b + 6) + (b - 18) = b - b - 6 + b - 18 = b - 24
-7(m - 4) + 5(m + 2) = -7m + 28 + 5m + 10 = -2m + 38
Ответ: 1) 14ab; 2) 6a - 11b; 3) b - 24; 4) -2m + 38