At a T-shirt stand on the boardwalk, 5 of the last 15 shirts sold were gray. Considering this data, how many of the next 12 shirts sold would you expect to be gray?

Can someone me do math because i am having a breakdown rn because i don’t get 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.

Avery’s piggy bank has 300 nickels, 450 pennies, and 150 dimes. she randomly picks three coins. each time she picks a coin, she makes a note of it and puts it back into the piggy bank before picking the next coin.