Now to factor, we must find what multiplies to -12, but adds to get -4. I can tell you know, the numbers are -6 and 2 (Through time you will learn to get faster with factoring)
Now we set it up as so:
(x-6)(x+2) = 0
Now to find the solutions, you must find how to get each set of parenthesis equal to 0. x-6=0 x=6 is a solution