Keep in mind that Time=Distance/Speed
Ambulance:
Since the ambulance travels 40 mph, that would be the speed
Since the ambulance travels 20 miles with 0 stops that would be the distance
\(\frac{40}{20}=2\)
The ambulance takes 2 hours to make its journey
Helicopter:
Since the helicopter travels 1 mpm, that would be the speed.
Since the helicopter travels 15 miles, that would be the distance
\(\frac{15}{1}=15\)
The helicopter gets to the hospital in 15 minutes
We can add the 3 minutes for takeoff and landing and that adds 6 minutes to the journey
\(15+6=21\)
The helicopter takes 21 minutes to complete the journey
Since the ambulance takes 2 hours or 120 minutes and the helicopter takes 21 minutes:
\(120-21=99\)
The helicopter will get there in \(99 \) fewer minutes.
Hope this helped!!!
-Ako