Find the Greatest number that will divide 100,126,148 without leaving

Pls , the question is in the picture!

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?

What is the sum of the first 8 terms of the geometric series