Suppose y varies directly as x and y= 7 when x = 2. find y when x = 21

The number of fish in a lake can be modeled by the exponential regression equation y=14.08 x 2.08^x where x represents the year

If t17 = 3 (t5) in an arithmetic progression, find t1 in terms of d.

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.