A. 10x(2y-10) B. (x+5)×(5x-1) C. (7-2x) ×(2x-7)

a) 10 × (2y - 10)
= 20y - 100

b) (x + 5)(5x - 1)
= 5x² + 25x - x - 5
= 5x² + 24x - 5

c) (7 - 2x)(2x - 7)
= 14x - 4x² - 49 + 14x
= - 4x² + 28x - 49

A). 10x (2y -10)
= 10x.2y +10x.-10
= 20xy -100x

B). (x +5)×(5x -1)
= x.5x +x.-1 +5.5x +5.-1
= 5x² -x +25x -5
= 5x² +24x -5

C). (7 -2x)×(2x -7)
= 7.2x +7.-7 -2x.2x -2x.-7
= 14x -49 -4x² +14x
= -4x² +14x +14x -49
= -4x² +28x -49

*maaf jika salah, semoga membantu ^_^