By moving -4 to the right hand side, we get

Now, by the properties of the absolute values, this last equation becomes in 2 conditions:

From condition a), by moving 12 to the right hand side, we get

and x is given by

Now, from condition b), by moving 12 to the right hand side, we have

then, x is given by

Therefore, the answer is the union of both solution, that is, the answer is the third option: x=-1, 9