a, b and e
a.
x + 5 = 8 ( subtract 5 from both sides )
x = 3
b
4x = 12 ( divide both sides by 4 )
x = 3
c
[tex]\frac{x}{9}[/tex] = 3 ( multiply both sides by 9 )
x = 27
d
x - 5 = 10 ( add 5 to both sides )
x = 15
e
[tex]\frac{x}{1}[/tex] = 3
note that [tex]\frac{x}{1}[/tex] = x, hence
x = 3
