A large bag of sand weighs 70 pounds. The bag weighs 5 pounds less than the weight of 4 small
boxes of sand. Which equation can be used to
find the weight w, in pounds, of each small box of
sand?

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.