1. Factor x^2+9x+20
((x+4)(x+5))/(x+3)*(x^2-x-12)/(x^2+3x-4)
2. Factor x^2-x-12
((x+4)(x+5))(x+3)*((x-4)(x+3)/(x^2+3x-4)
3. Factor x^2+3x-4
((x+4)(x+5))/(x+3)*((x-4)(x+3))/((x-1)(x+4))
4. Simplify
((x+4)(x+5)(x-4)(x+3))/((x+3)(x-1)(x+4))
5. Cancel x+3
((x+5)(x-4))/(x-1)
Have a nice day
