Rusty has 3 cars for every 9 trucks it owns. if the company owns 31 cars, how many trucks do the company own?

Based on what i know about mean, this doesn't add up.

An equation where variables are used to represent known values—function notation true or false

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?