Simplifying
12x + 0 = 144

Reorder the terms:
0 + 12x = 144
Remove the zero:
12x = 144

Solving
12x = 144

Solving for variable 'x'.

Move all terms containing x to the left, all other terms to the right.

Divide each side by '12'.
x = 12

Simplifying
x = 12