First person gets brainliest 3

If f(x)= 3x+6 which of the following is the inverse of f(x)

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?

How do you solving the solution of each system using elimination?