Answer: f ≤ 17
Explanation:
She only has 17 sheets of paper, so you can eliminate f > 17 and f ≥ 17 easily.
The problem states that she'd be using some of the paper. This doesn't mean that she's going to use all of it, but she can.
Because we don't know how much she's going to use, your answer would be f ≤ 17.