Gil is reading a book that has a total of 268 pages. He has already read part of the book during the first week of school. During the second week of school he read three times as many pages as
the first week. During the third week, he finishes the book, reading 18 more pages than the first
week. How many pages did he read in the first week?

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.