Question 1127384
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The time equation is


    {{{7/(x-5)}}} = {{{17/(x+5)}}}.


    7*(x+5) = 17*(x-5)

    7x +35 = 17x - 85

    35 + 85 = 17x - 7x

    120 = 10x

    x = 120/10 = 12.


<U>Answer</U>.  The speed of the boat in still water is 12 miles per hour.
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Solved.