Let's break down the problem:

1. Initial Speed Calculation:

   • They covered 14 miles in 2 hours.
   • The speed is calculated as: $\text{Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{14 \text{ miles}}{2 \text{ hours}} = 7 \text{ miles per hour (mph)}$

2. Reduced Speed:

   • They reduced their speed by 2 mph, so their new speed is: $\text{New Speed} = 7 \text{ mph} - 2 \text{ mph} = 5 \text{ mph}$

3. Time Calculation for Remaining Distance:

   • They have 15 miles left to travel.
   • The time taken to cover this distance at the reduced speed is: $\text{Time} = \frac{\text{Distance}}{\text{Speed}} = \frac{15 \text{ miles}}{5 \text{ mph}} = 3 \text{ hours}$

Therefore, it took them 3 hours to cover the remaining 15 miles.

Would you like further details on any part of this calculation, or have any questions?

Here are some related questions you might find interesting:

1. How long would it have taken to travel the remaining distance at their original speed?
2. What was their average speed for the entire trip?
3. How far would they travel in 1 hour at their reduced speed?
4. If they had not reduced their speed, how much time would they have saved?
5. What would their speed be if they reduced it by another 2 mph?
6. How much longer would it take if they further reduced their speed by 1 mph?
7. How long would the entire trip take if they started at their reduced speed?
8. What would be the total distance traveled in 5 hours at the reduced speed?

Tip: Always double-check your calculations, especially when dealing with multiple steps in word problems.