The second step in the process for factoring the trinomial is to:

Example:  the second step in the process for factoring the trinomial x^2-3x-40 is to: Well you really should find the sum of the factors of −40 (not 40) 
But before you can do that, you need to LIST the factors of −40 (not 40) 
−1 * 40 
−2 * 20 
−4 * 10 
−5 * 8 
−8 * 5 
−10 * 4 
−20 * 2 
−40 * 1 

NOW we find the sum of the factors of −40 
−1 + 40 = 39 
−2 + 20 = 18 
−4 + 10 = 6 
−5 + 8 = 3 
−8 + 5 = −3 
−10 + 4 = −6 
−20 + 2 = −18 
−40 + 1 = −39 

Then we choose the factors of −40 whose sum is −3 ---> −8 and 5 
x^2 − 3x − 40 = (x − 8) (x + 5) 

So FIRST step is B, SECOND step is C, and final step is factoring. 
What Rita did was combine these 2 steps together, which you will learn to do as you get better at factoring.