Can someone help me with number 16?

Answer:
Step-by-step explanation:
if we take from south to north as y-axis,west to east as x-axis.
Then position of helicopters are (-20,0) and (15,-15)
a.d=√((15+20)²+(-15-0)²)=√(1225+225)=√1500=10√15
b.
origin is place of rally.
one helicopter is 20 miles south of rally.
other helicopter is at distance=√(15²+15²)=15√2 miles SE of rally.
c.
time taken by first helicopter=(20/80)×60=15 minutes
second helicopter takes time=(15√2/80)×60=(45√2)/4≈15.91 minutes.