Given,
The boat travels at an speed of 65 miles per hour.
Which means, the boat is travelling 65 miles in 1 hour.
So,
Using unitary method,
In 1 hour, the boat travels 65 miles.
In 3 hour, the boat travels (65 * 3) miles.
= 195 miles.
So, The boat travels 195 miles in 3 hours at 65 miles per hour.