I don’t really understand this

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?

Complete the solution of the equation. find the value of y when x equals -5. -4x - 8y = -52

1) prove that 731^3−631^3 is divisible by 100 2) prove that 99^3−74^3 is divisible by 25