Find equations of the spheres with center (2,-3,6) that touch (a) the xy plane, (b) yz plane, (c) the xz plane.

Find the midpoint of the segment with the given endpoint k(-4,4) and l(6,12)

Match each inequality to the number line that represents its solution

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.