Denote points:
These three points lie on the same line in order M, G and S. The distance MS=341 mi and MS=GM+GS.
It takes Doug 3 hours to go to a motel from gas station (GM) and it takes 2.5 hours Ashley to go to a sister's home from gas station (GS). The total time is 3+2.5=5.5 hours.
Then using the formula d=rt, you can conclude that
341=5.5·r,
r=341:5.5,
r=62 mi/h.
Answer: 62 mi/h.