Answer:
3 mph
Step-by-step explanation:
Let the speed of the river's current be x
Upstream (against the river's current)
Resultant velocity = 6 - x
Distance covered = (6-x)t
10.5 = (6-x)t
t = 10.5/(6-x)
Downstream (with the river's current)
Resultant velocity = 6+x
Distance covered = (6+x)t
t = 31.5/(6+x)
Therefore.......
10.5/(6-x) = 31.5/(6+x)
10.5(6+x) = 31.5(6-x)
63 + 10.5x = 189 - 31.5x
Collect like terms
42x = 126
x = 3 miles per hour
HOPE IT HELPS!
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