Question 83625
Formula is D = r x t


Down stream = r + c
Upstream    = r - c


Distance = 84 mile w/c is the same in both Up and Downstream


Time = Up 6 hrs

Time = Down 2 hrs


The equation is;


84 = (r + c)* 2 Downstream

84 = (r - c)* 6 Upstream
 

   (84 = 2r + 2c)*-3     ( since you want to solve for the current, eliminate r
    84 = 6r - 6c           by multiplying -3)


   -252 = -6r - 6c
     84 =  6r - 6c


 It yields -168 = -12 c     devide both by -12 to get the value of c


            c = 14 mph      that's the speed of the stream

  

Hope this will help you.  Johnsen P