Solve the equation. -3x + 7 = -21​

Which of these choices show a pair of equivalent expressions?

Which is the correct first step in finding the area of the base of a cylinder with a volume of 26x cubic meters and a height of 6.5 meters? v=bh 6.5=b(26x) v=bh v=26pi+(6.5) v=bh v=26pi(6.5) v=bh 26pi=b(6.5)

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.