20 points. A triangle has an exterior angle with a measure of 120°. Can you determine the measures of the interior angles? The answer is no, I just need an explanation why, thank you :)

(c) the diagram shows the first three shapes of a matchsticks arrangement.first shape = 3second shape = 5third shape = 7given m represents the number of matchstick used to arrange the n'th shape.(i) write a formula to represent the relation between m and n. express m as the subjectof the formula.(ii) 19 matchsticks are used to make the p'th shape. find the value of p.