Answer:
(3x-4)(x+5)
Step-by-step explanation: First set up a diamond problem. Find what two numbers add to 60 since 3*20 and add to -11. That would be 15 and -4. Then draw a 2x2 box, and put in 3x^2 the -20, 15x and -4x. Then find the factors. Hope that helped! :)