The answer is 121,434,796.00165
We calculate both velocities:
upstream 8 miles in 2 hours = 4 miles / hour
downstream 8 miles in 1 hour = 8 miles / hour
ps -stream speed = 4 mph
ps + stream speed = 8 mph
Adding both equations
2 ps = 12 mph
paddling speed = 6 mph
stream speed = 2 mph
It would be 1/3rd because your last number would be 4 in the equation of 12 sandwiches.
