Solve the problem. make sure your answer is in simplest form and improper fractions are expressed as mixed numbers. a. 7/10b.14/15 c.10/21 d.7/21will give brainliest

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

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.

∠1 and ∠2 are vertical angles. ∠2 has a measure of 63°. what is the measure of ∠1 ? enter your answer in the box.