4m-15n+13m+18n вырожение -2(x-3)+4+(x+1) b+(7--8)

-4m - 15n + 13m + 18n = (13m - 4m) + (18n - 15n) = 9m + 3n 
-2(х - 3) + 4 + (х + 1) = - 2х + 6 + 4 + х + 1 = -х + 11
b + (7 - b) - (13 - 8) = b + 7 - b - 13 + 8 = (b - b) + (7 + 8 - 13) = 2