The ambulance has 20 miles to travel and goes at 40 mph so it would take 30 minutes to go to the hospital
A helicopter has to go 15 miles to get to the hospital and goes at 1 MPH so it'd take 15 minutes but it takes 3 minutes for takoff and landing which would be added to a sum of 6. The helicopter then would take 15+6 minutes which is 21, 30-21 you get 9
So 9 minutes is the answer
Hope this helps!