Answer:
60 miles
Step-by-step explanation:
We assume the trip is "d" miles and that the "extra hour" refers to the additional time that a current of 2 mph would add. That is, we assume the reference time is for a current of 0 mph.
The time with no current is ...
time1 = distance/speed
time1 = d/12 . . . . hours
With a current of 2 mph in the opposite direction, the time is ...
time2 = d/(12 -2) = d/10
The second time is 1 hour longer than the first, so we have ...
time2 = 1 + time1
d/10 = 1 + d/12
6d = 60 + 5d . . . . multiply by 60
d = 60 . . . . . . . . . subtract 5d
The one-way distance is 60 miles.
