4. Mrs. Magee's class is collecting books to donate to the local library. The
class goal is to collect 60 books for the youth section, and Mrs. Magee's
student's have donated 15 books already. They plan to donate 3 more books
every week until they reach their goal. Which of the following could be used
to determine w, the number of additional weeks that Mrs. Magee's class
collects books?