Answer:
6 h
Explanation:
The relation between time, speed, and distance is ...
time = distance / speed
The total time for the two segments of her ride will be the sum of the times for each of the segments.
__
first 9 miles
t1 = (9 miles)/(3 mi/h) = 3 h
last 6 miles
After riding 9 miles of the 15-mile distance, Dana had 15 -9 = 6 miles to go.
t2 = (6 miles)/(2 mi/h) = 3 h
total time
The total time required for the distance of 15 miles is ...
t1 +t2 = (3 h) +(3 h) = 6 h
It took 6 hours for Dana to cover the distance.