A - (a - (a-4))

7x * ((y-x) + 3y)

4y - (3y + (2y (y+1)))

5c - (2c - ((b-c) - 2b))

A - (a - (a-4)) = a - (a-a+4) = a-a+a-4=a-4

7x * ((y-x) + 3y) = 7x (4y-x) = 28xy-7x³

4y - (3y + (2y (y+1))) = 4y - (3y+2y²+2y) =

4y-3y-2y²-2y=-2y²-y

5c - (2c - ((b-c) - 2b)) = 5c - (2c-b+c-2b) =

5c-2c+b-c+2b=2c+3b