:b(m-7)-7b x(c+1)+c(x-1) y(x-4)+x(3-y) m(k-3)-k(m-5) a(1-b)-a(1+b) b(2d-5)-b(d+5)

B(m-7)-7b=bm-7b-7b=bm-14b
x(c+1)+c(x-1)=xc+x+xc-c=xc+x-c
y(x-4)+x(3-y)=xy-4y+3x-xy=3x-4y
m(k-3)-k(m-5)=mk-3m-mk+5k=5k-3m
a(1-b)-a(1+b)=a-ab-a-ab=-2ab
b(2d-5)-b(d+5)=2bd-5b-bd-5b=bd-10bd