AMC 12 2009b Problem 2

Paula the painter had just enough paint for $30$ identically sized rooms. Unfortunately, on the way to work, three cans of paint fell off her truck, so she had only enough paint for $25$ rooms. How many cans of paint did she use for the $25$ rooms?

\textbf{(A)}\ 10 \textbf{(B)}\ 12 \textbf{(C)}\ 15 \textbf{(D)}\ 18 \textbf{(E)}\ 25