Question 911667
_______________rate__________time__________distance
UP_____________8-c___________(1.5)t________d
DOWN___________8+c___________t_____________d


t is the time to go downstream for distance d.
c is speed of the river current.
d is the specifiable distance.
The unknown variables are t and c.


Upstream is against the current, so is less a rate and takes MORE TIME.
The same distance d for both directions in the description.


This specific problem does not have a unique solution.
{{{(3/2)(8-c)t=d}}} and {{{(8+c)t=d}}},  and since those are two formulas for d, {{{highlight((3/2)(8-c)t=(8+c)t)}}}.


If you knew something more about time, you could solve for c.