What is the missing reason in the proof

Idon’t understand! use slope intercept form to solve: through: (2,5) slope= undefined

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.

In the diagram below, abc is congruent to dec what is the value of x