Eliana is reading a 964-page book.She reads 20 pages per day in the book. If x represents the number of days Eliana has spent reading the book so far, which of the following equations can be used to find the number of pages remaining in the book for Elaina to read. A-y=20x+964 B-y=-20+964 C-y=964+20 D-y=-964+20