A boat requires four hours to travel a given distance upstream against a five mile per hour current, but only requires three hours to travel downstream with that same current back to the dock. Find the speed of the boat in still water.
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Question

A boat requires four hours to travel a given distance upstream against a five mile per hour current, but only requires three hours to travel downstream with that same current back to the dock.  Find the speed of the boat in still water.  
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anonymous · Answer

d=4(x-5)
d=3(x+5)
4(x-5)=3(x+5)
solve for x

anonymous · Answer

4x-20=3x+15
x=15+20=35