We can solve this problem by the rule of three.
762.5 miles---------------------5 hours
x-----------------------------------3 hours
x=(762.5 miles x 3 hours) / 5 hours=457.5 miles.
Answer: this plane would travel in 3 hours 457.5 miles.
Other method:
We can calculate the plane´s speed.
speed=distance /time.
speed=762.5 miles/5 hours=152.5 miles /hour
distance= speed x time
distance=(152.5 miles/hour)(3 hours)=457.5 miles.
Answer: this plane would travel in 3 hours 457.5 miles.