Answer:
The problem does not work.
Step-by-step explanation:
The plane with speed of 31 mph will cover 640 miles in hours.
Now, it burns 5 gallons of gas every 3 minutes i.e. 0.05 hours.
So, it will burn in 20.64 hours gallons.
Now, the helicopter with speed of 45 mph will cover 640 miles in hours.
Now, it burns 7 gallons of gas every 5 minutes i.e. 0.083 hours.
So, it will burn in 14.22 hours gallons.
But both of them starts with only 80 gallons of fuel.
Therefore, the problem does not work. (Answer)