Students per class

Question

There are two times as many people in the Psychology class as in the art history class. There are 15 More people in the algebra class then in art history class. The total enrollment of the three classes is 63 students. How much students are enrolled in each class?

Answer 1

Let x be number in art history class. Then x + 15 is number in algebra class. and 2x in the psychology class.  Add these up and set equal to 63. Solve for x. Plug back in expressions to find amount for each class