John reads an equal number of pages of a book every week. The graph below shows the number of pages of the book left to read, y, after x weeks: A graph titled Johns Book Reading shows Number of Weeks on the x axis and Number of Pages Left on the y axis. The scale on the x axis shows numbers from 0 to 6 at increments of 1, and the scale on the y axis shows numbers from 0 to 175 at increments of 25. A straight line joins the ordered pairs 0, 125 and 1, 100 and 2, 75 and 3, 50 and 4, 25 and 5, 0. Which equation best models the relationship between x and y? y = −5x + 25 y = −25x + 125 y = −25x + 175 y = −5x + 125