A fishing boat left Diego Garcia and traveled toward Madagascar at an average speed of 15 km/h. A cruise ship left at the same time and traveled in the opposite direction with an average speed of 19 km/h. Find the number of hours the cruise ship needs to travel before the ships are 204 km apart.
We can consider the relative speed of the two ships as the sum of their speeds, which is $15+19=34$ km/h. To find the number of hours the cruise ship needs to travel before the ships are 204 km apart, we can set up the equation: \begin{align*}
34t&=204\\
t&=\frac{204}{34}\\
t&=\boxed{6}.
\end{align*}