The number of books that can be shelved is 45. So then we know that the amount that need to be shelved can be 45, if the bookshelf had 0 books on it. This means that it can have the equal part of the inequality sign.
However, the amount of book that need to be shelved cannot exceed 45, so b must be less than 45.
Therefore, the answer must be D) b ≤ 45.
