−1.5(4−n)+2.8 how to solve this problem

Look at the following graph of the given equation. determine whether the equation is a function. explain why or why not.

Twelve less than a number is at most 20

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.