2024 AMC 8 Problem 21

A group of frogs (called an army) is living in a tree. A frog turns green when in the shade and turns yellow when in the sun. Initially, the ratio of green to yellow frogs was 3 : 1. Then 3 green frogs moved to the sunny side and 5 yellow frogs moved to the shady side. Now the ratio is 4 : 1. What is the difference between the number of green frogs and yellow frogs now?

\textbf{(A)} 10 \qquad \textbf{(B)} 12 \qquad \textbf{(C)} 16 \qquad \textbf{(D)} 20 \qquad \textbf{(E)} 24

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.