Simplify completely (x^2+x-12)/(x^2-x-20)÷(3x^2-24+45)/ (12x^2-48x-60)

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)