Tìm x : a) (7x-35).(-4x-20)=0 b) -12+2(-x+7)=-18 c) 95-5.(-24-x)=-5 TOÁN 6 ạ.

a) (7x-35).(-4x-20)=0

=>\(\left[ \begin{array}{1}7x-35=0\\(-4)x-20=0\end{array} \right.\) 

=>\(\left[ \begin{array}{l}x=5\\x=-5\end{array} \right.\)

b) -12+2(-x+7)=-18

=>2×(-x+7)=(-12)+(-18)

=>2×(-x+7)=-30

=>-x+7=-30÷2

=>-x+7=-15

=>-x=-15-7

=>-x=-22

=>x=22

c,95-5.(-24-x)=-5

=>5×(-24-x)=95-(-5)

=>5×(-24-x)=-100

=>(-24-x)=5×(-100)

=>(-24-x)=-500

=>-x=(-24)-(-500)

=>-x=-524

=>x=524