Will give brainliest for right answer only!

What is the measure of ac? 5 units 13 units 26 units 39 units 3x- 2b 6x + 9

What is the value of m in the equation 1/2 m - 3/4n=16 when n=8

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.