Ответ:

7.-0,6x=-0,3

-0,6x:(-0,6)=-0,3:(-0,6)

x=-0,3:(-0,6)

x=0,5

8.-4/7x=-16/21

-7/4*(-4/7)x=-7/4*(-16/21)

7/4*4/7x=-7/4*(-16/21)

1/4*4x=-7/4*(-16/21)

x=-7/4*(-16/21)

x=7/4*16/21

x=7*4/21

x=4/3

9.-16(x-7)=-48

x-7=3

x=3+7

x=10

10.7(5-x)-3(x+4)=63

35-7x-3(x+4)=63

35-7x-3x-12=63

23-7x-3=63

23-10x=63

-10x=63-23

-10x=40

x=-4