a) 7x + 5 - x + 8 = 31
7x - x = 31 - 5 - 8
6x = 26 - 8
6x = 18
x = 18/6
x = 3
b) 5.(3x - 2x) = 55
15x - 10x = 55
5x = 55
x = 55/5
x = 11
c) 27 = 3.(x + 3)
27 = 3x + 9
- 3x = 9 - 27
- 3x = - 18 .(-1)
3x = 18
x = 18/3
x = 6
d) 16x + 2.(7x + 8) - 9 = 67
16x + 14x + 16 - 9 = 67
16x + 14x = 67 + 9 - 16
2x = 58 - 16
2x = 42
x = 42/2
x = 21
e) 12 - 7.(3x + 6) - 5 = 70
12 - 21x - 42 - 5 = 70
- 21x = 70 - 12 + 42 + 5
- 21x = 58 + 42 + 5
- 21x = 100 + 5
- 21x = 105 .(-1)
21x = - 105
x = - 105/21
x = - 5