How do I solve this?

Just like any other equations with one variable:

X + X/2 -4 = X/4

Move variables to one side, and constants to other.

X + X/2 - X/4 = 4

Multiply both sides by 4

4X + 2X - x = 16

5X = 16

X = 16/ 5 = 3 1/5 = 3.2