3(x = 4) = 36
I am assuming that you made a typo and meant 3(x - 4) = 36..? :)
If so, then simply simplify.
3(x - 4) = 36
3x - 12 = 36
Add 12 to both sides.
3x = 36 + 12
Simplify.
3x = 48
Divide both sides by 3.
x = 48/3
Simplify.
x = 16
~Hope I helped!~