Question 36034
Let the speed of theboat in still water be x
{{{60/(x+3)+60/(x-3)=9}}}
60[(x-3)+(x+3)]=9[(x+3)(x-3)]
{{{60(2x)=9(x^2-9)}}}
{{{120x=9x^2-81}}}
{{{9x^2-120x-81=0}}}
SOlve that: you get x=13.9 
Hence, the speed is 13.9mph in still wate.r
Paul.