The sequence follows a minus 3 pattern: 12, 9, 6, 3, (write a formula for the nth term of the sequence, be sure to specify what value of n your formula starts with.)

In the 30-60-90 triangle below side s has a length of and side r has a length

Name each raycalculation tip: in ray "ab", a is the endpoint of the ray.

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.