9is 18% of what?me out on this.

The perimeter of a movie screen is 54 meters. the screen is 18 meters wide. how tall is it?

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.

How can you find the magnitude of a vector, v = < x,y > , where the horizontal change is x and the vertical change is y?