Richard is hooked on a new book series, The Galaxy. Each book in the series is the same length and chronicles a different year in the Waka Waka Galaxy. Richard has cleared off the top shelf of his bookcase to leave room for each of the books as they come out. Each book takes up 1 inch of space along the shelf. There is a proportional relationship between the number of books on the shelf, x, and how much shelf space the books take up (in inches), y.