Hey there!
Putting it int he form of ax^2+bx+c would give you:
x^2+9x+20 = 0 because you add the 9x to the other side and rearrange the terms.
Now, the next step in solving means we have to factor it. We want two numbers that add to 9 and multiply to 20. These numbers are 5 and 4. Therefore, your answer is:
(x+5)(x+4) = 0
The answer is C.
Hope this helps!