7.

2(9x – 5) – 6(x + 2) = 4(x + 6)

18x – 10 – 6x – 12 = 4x + 24

18x – 6x – 4x = 24 + 10 + 12

8x = 46

x = 46 / 8 = 23 / 4

8.

7x – 3 = 18

7x = 18 + 3

7x = 21

x = 21 / 7 = 3

9.

6x + 12 = 0

6x = –12

x = –12 / 6 = –2