Several years ago I averaged 8 MPH riding in the mountains hereabouts: I could ride a 32 mile loop in 4 hours, or extend it to a 40 mile loop in 5 hours.

More recently, the bike computer shows an 8.5MPH average when riding to and returning from a grocery store in the next mountain town over.

And some commute type riding in a flat urban area: I've covered just under 14 miles in an elapsed time of right on an hour. (Start the ride at 4:59PM, walk into a restaurant at 6:01PM.) I've ridden a different route, same endpoints, that's 16 miles but with some longer uninterrupted stretches also in the same hour. Note that this is urban riding complete with waiting at red lights. I leave it as an exercise for the reader to figure out what my cruising speed must be to compensate for the lost time.