-4,2x * (-6y) = 25,2xy
8m + 5p - 13m - p = 8m - 13m + 5p - p = -5m + 4p
k - (17 - k) + (-k + 30) = k - 17 + k - k + 30 = k + 13
-6(4 + a) + 8(a - 6) = -24 - 6a + 8a - 48 = 2a - 72
Ответ: 1) 25,2xy; 2) -5m + 4p; 3) k + 13; 4) 2a - 72