Answer: 239.0025 miles.
Explanation:
First we have the relationship:
Distance = speed*time.
Because how it is worded, i guess that the boat can mantain a constant speed of 318.67 mph for 0.75 hours.
Then, we have the speed and the time, with those values we can find the distance.
speed = 318.67 mph
Time = 0.75 hours.
Distance = 318.67 mph*0.75h = 239.0025 miles.