a(x+y)+a(b-x) = a(x+y+b-x) = a(y+b)
b(2x-5y)-b(3x-y) = b(2x-5y-3x+y) = b(-x-4y)
2c(a+b)+c(5a-3b) = 2c(a+b)+c(5a-3b) = 2ca+2cb+5ac-3bc = 2ca+5ac+2cb-3bc = ac(2+5)+bc(2-3) = 7ac-3bc
x(2x+7y)-x(3x-5y) = x(2x+7y-3x+5y) = x(2x-3x+7y+5y) = x(-x+12y)
a(x+y)+a(b-x) = a(x+y+b-x) = a(y+b)
b(2x-5y)-b(3x-y) = b(2x-5y-3x+y) = b(-x-4y)
2c(a+b)+c(5a-3b) = 2c(a+b)+c(5a-3b) = 2ca+2cb+5ac-3bc = 2ca+5ac+2cb-3bc = ac(2+5)+bc(2-3) = 7ac-3bc
x(2x+7y)-x(3x-5y) = x(2x+7y-3x+5y) = x(2x-3x+7y+5y) = x(-x+12y)