Answer:
15 hours
Step-by-step explanation:
Given:
Fernell's speed mph
Dabney's speed mph
Denote:
- distance covered by Fernell
- distance covered by Dabney
- Fernell's time
- Dabney's time
1. If Fernell drove for 3 hours longer than Dabney, then his time is 3 hours more than Dabney's time and
2. If Fernell covered 18 miles less than Dabney, then
Use formula
Subtract from the first equation the second equation and equate it to 18: