To find out how far the cruise ship sailed, you can use the formula:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]
In this case, the speed is 18 miles per hour, and the time is 9 hours.
\[ \text{Distance} = 18 \text{ miles/hour} \times 9 \text{ hours} = 162 \text{ miles} \]
So, the cruise ship sailed 162 miles.