Can someone explain to me how this is done

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?

The length of a rectangle is 2 inches more than twice it’s width. if the perimeter of the rectangle is 70 inches, find it’s length and width

How do you solve this step by step?