Chapter 9.4, Problem 16P

At a frog exhibit, $\frac{3}{5}$ of the frogs are bullfrogs, $\frac{2}{3}$ of the remainder are tree frogs, and the rest are river frogs. There are ,36 bulfrogs in the exhibit. How many river frogs are there?“ Solve this problem in two ways: with the aid of a diagram and with algebraic equations. Explain both solution methods, and discuss how they are related.