Mohon dibantu ya teman teman no 1(a,b,c)

A. 10(2y-10) = 0
20y-100 = 0
Y =100/20
Y = 5
B.(x+5) (5x-1)
5X²-x+25x-5
5x²+24x-5
X = - 5 x=1/5
C. (7-2x) (2x-7)
14x-49-4x²+14x
- 4x²+28x-49
4x²-28x+49
X=7/2 x=7/2