To simplify the expression, we can check if there are terms that are needed to be added or subtracted. In this case, there are none. We get the factors of 4 equations present in the expression.
x^2+x-12 = {3,-4}
x^2-x-20 = {5,-4}
3x^2-24+45 = {5,3}
12x^2-48x-60 = {5,-1}
hence we cancel 5 and from numerator and denominator.
the answer is (x+4)^2/ (x-5)*(x+1)