Question 1202570
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<pre>

Write the time equation


    {{{d/3}}} + {{{d/7}}} = 10 hours.


Here d is one way distance, and the terms in the left side 
represent time to the pond and back, respectively.


To solve equation, multiply both sides by 3*7.  You will get

    7d + 3d = 10*3*7

      10d   = 10*3*7

        d   =  3*7 = 21.


<U>ANSWER</U>.  The one-way distance is 21 miles.


<U>CHECK</U>.  Time to get pond is  {{{21/3}}} = 7 hours.

        Time to return back is  {{{21/7}}} = 3 hours.

        Total time is  7 + 3 = 10 hours.   ! correct !
</pre>

Solved.