I believe the answer is C, as it would fit all the criteria needed to have to answer a question like it, for example: The question must include what it equals (obviously) on one side, it must also have x^2, once again, all of them do. However, there must be + 3x to account for the longer side (if x=2 and one side is 3 feet wider than the length then 4+6=10, if x=3 then 9+9=18 and so on) which C, B, and D all have. Finally, there must be an account for y, which would require subtracting y from the total area, which is only in C.