How do I solve this?

Solve - pv + 40 < 65 for v solve 7w - 3r = 15 for r

Mrs. morton has a special reward system for her class. when all her students behave well, she rewards them by putting 3 marbles into a marble jar. when the jar has 100 or more marbles, the students have a party. right now, the the jar has 24 marbles. how could mrs. morton reward the class in order for the students to have a party?

Cody was 165cm tall on the first day of school this year, which was 10% taller than he was on the first day of school last year.