Using the distribution method:
x^2 + 12x - 8x = 14 + x^2 - 4x
x^2 + 4x = x^2 - 4x + 14
Now, I'm isolating x by moving all the x's onto one side of the equation:
x^2 - x^2 + 4x + 4x = 14
Combine like terms (x^2 cancels out):
8x = 14
x = 14/8
Simplified: x = 7/4