Question 1066350
<pre>
               SPEED        TIME           DISTANCE

DOWN           r+20         {{{50/(r+20)}}}             50

UP             r-20         {{{50/(r-20)}}}             50

TOTAL                     {{{3&1/3}}}
</pre>


Solve this for r.
{{{50/(r+20)+50/(r-20)=3&1/3}}}