We have the following:
d dollars is the total amount of dollars that all the books cost, and b is the number of books that were purchased.
Therefore, to know what a book costs, we must divide the total amount in dollars by the number of books there are, which would be the following:
![(d)/(b)](https://img.qammunity.org/2023/formulas/mathematics/college/3g9d4ojttkfgszhshiklsbvq99kpombazv.png)
Therefore, the answer is B. d/b