Help please been stuck on this

Maria walks a round trip of 0.75 mile to school every day.how many miles will she walk in 4.5 days

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.

Find the measure of angle a in the following triangle