Pls help meee fellow high schoolers

Find the slope of the line that contains the following points. r(-2, 4), s(6, -2)

Solve the system of equations y= 3/2 - 1, -x+ y =-3

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.