PreCal Questions Help Please

Perform the indicated operation and reduce completely

3 / (x^2 - x - 20) + x / (x^2 - 8x + 15) - x / (x^2 + x - 12)

I was trying to simplify using common denominator but it just got so complicated. Can anyone help?

First we should factor those denominators so our expression looks like this;
3/[(x-5)(x+4)] + x/[(x-5)(x-3)] - x/[(x+4)(x-3)]
Then we see that our common denominator could be (x-5)(x+4)(x-3), so we have
3(x-3)/[(x-5)(x+4)(x-3)] + x(x+4)/[(x-5)(x+4)(x-3)] - x(x-5)/[(x-5)(x+4)(x-3)]
= (12x-9)/[(x-5)(x+4)(x-3)]
= 3(x-3)/[(x-5)(x+4)(x-3)]
(x-3) cancels
= 3/(x-5)(x+4) is the simplified answer

i was able to get a common denominator of (x-5)(x+4)(x-3) by factoring the equations.
final answer: 12x-9/(x-5)(x+4)(x-3)