How do u solve this promblem? z=-3a-2, for a

Acircle has a circumference of 28.36 units what is the diameter of the circle

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 value of the variable and the length of each chord for #5 and #6.