For this question, you will now need to solve for both a and b, you can break down the expression that they want you to find:
(a^2-b^2)/(a-b)
= (a+b)(a-b)/(a-b) (Difference of squares)
= a+b (The (a-b) is common at the top and bottom so they will cancel
Now a+b =
Therefore the answer is (C)