5x = - 20
[tex] \frac{5x}{5} [/tex] = [tex] \frac{-20}{5} [/tex]
x = - 4
b) 5 + x = 20
5 + x - 5 = 20 - 5
x = 15
c) [tex] \frac{x}{5} [/tex] = -20
[tex] \frac{x}{5} [/tex] × 5 = - 20 × 5
x = - 100
d) x + 8 = 0
x + 8 - 8 = 0 - 8
x = - 8
e) 9x = 0
[tex] \frac{9x}{9} [/tex] = 0/9
x = 0
f) 3x - 7 = 0
3x - 7 + 7 = 0 + 7
3x = 7
(3x) / 3 = 7/3
x = [tex] \frac{7}{3} [/tex]