



 
Hi Sonja, Suppose that the speed of the boat in still water is b miles per hour and the speed of the current in the river is c miles per hour. Then for the trip downstream the boat travels at (b + c) miles per hour. Since distance = time rate we can conclude that
On the return trip the boat travels at (b  c) miles per hour and hence
Hence you have a pair of equations to solve
Since you want b I would eliminate c by multiplying the first equation by 2.5 and add the two resulting equations. I hope this helps,  


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