5a - 2 > 10 Can u do step by step and also show how you know that you found the correct a value

Triangle knm is what is true about the sides of knm

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.

State one method by which you can recognize a perfect square trinomial.