20 A = (5x) x 8x + (5-x) x 3x
B = (3x - 5)(1+ 2x) + 7x(3x - 5)
21 A= (2+ 3x) (x + 1) + (2 + 3x)(x + 4)
B = (4x + 3)(2x - 1) + (2x - 1)(5 - 2x)