100-121k^2=0 What are solutions to this equation?

What could explain what happened when the time was equal to 120 minutes

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?

For what values of x is x2 + 2x = 24 true?