Answer: (x - 4) (x - 5)
So since the last number in the trinomial (20) is positive, and the second number (-9x) is negative, this means both of the factors will be negative, so that means the answer is NOT C or D.
So you have to find two numbers that multiply to make 20 (last number) and that add to make -9 (second number).
So the answer is B, and have -4 and -5 because you multiply and get positive 20, and add and get -9.