Step-by-step explanation
We must solve for x the following equation:

1) Assuming x ≠ -3 and x ≠ -4, we multiply both sides both sides by (x + 3)(x + 4):

2) Applying the distribution property for the multiplication on the right side, we have:

3) Passing the x at the left as -x at the right, we have:

4) Passing the +12 at the right as -12 at the left, we have:

5) Finally, dividing both sides by 2, we get:

Answer
x = -2