Depends on a lot of things, how fit you are, how hard you're trying, where you're riding, what bike you're using and so on.
On easily ridden roads, a pack of racers could do it in about 4 hours. Riding solo, I'd need about 6. Some may need more.
The time it takes to bike 2 miles depends on your speed. On average, it takes about 10-15 minutes to bike 2 miles at a moderate pace.
The time it takes to bike 6 miles depends on your speed. On average, it takes about 30 minutes to bike 6 miles at a moderate pace of 12 miles per hour.
The time it takes to bike 80 miles depends on your speed. On average, a person biking at a moderate pace of 12-14 miles per hour would take about 5-7 hours to complete the 80-mile distance.
The time it takes to bike 17 miles depends on your speed. On average, it takes about 1 to 1.5 hours to bike 17 miles at a moderate pace of 12-15 miles per hour.
The time it takes to bike 60 miles depends on your speed. On average, it takes about 3-4 hours to bike 60 miles at a moderate pace of 15-20 miles per hour.
The time it takes to bike 8 miles depends on your speed. On average, it takes about 30-45 minutes to bike 8 miles at a moderate pace of 12-16 miles per hour.
The time it takes to bike 9 miles depends on your speed. On average, it takes about 30-45 minutes to bike 9 miles at a moderate pace of 12-15 miles per hour.
The time it takes to bike 14 miles depends on your speed. On average, it takes about 1 to 1.5 hours to bike 14 miles at a moderate pace of around 10-15 miles per hour.
The time it takes to bike 2 miles depends on your speed. On average, it would take about 10-15 minutes to bike 2 miles at a moderate pace of around 8-12 miles per hour.
The time it takes to bike 3 miles depends on your speed. On average, biking at a moderate pace of 12-14 miles per hour, it would take about 15-20 minutes to bike 3 miles.
The average bike is typically around 68 inches long.
I presume you mean how long will it take for a 12 miles bike ride. It depends on how fast you can bike, if it's uphill or downhill. The average is between 8-13 mph for most people to bike on a 10-speed on the whole. By that measurement, it could take 50-90 minutes or so on the average.