This question is ultimately asking you to factor 3x² - 9x - 30, which you can do by finding factors of 30 that, when one is multiplied by 3 due to the 3x², makes -9. These factors are 5 and 6, with 5 being multiplied by 3 so you get 15 and 6. Because you have -9, the 5 must be negative, which means the 6 is positive, so you get your final answer as:
(3x + 6)(x - 5)
I hope this helps!