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