Question 1168214
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<pre>

The "time" equation is 


    {{{d/(8-x)}}} = {{{3*(d/(8+x))}}},


where x is the unknown rate of the current;  d is the on way distance.


We can cancel the factor d in both sides.  Then we have


    {{{1/(8-x)}}} = {{{3/(8+x)}}}.


To solve this equation, first cross-multiply; then simplify


    8 + x = 3*(8-x)

    8 + x = 24 - 3x

    x + 3x = 24 - 8

    4x     = 16

     x     = 16/4 = 4.


<U>ANSWER</U>.  The rate of the current is 4 km/h.
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Solved.