Question 1189181
<pre>
                   SPEED     TIME                DISTANCE

downstream         r+3       18/(r+3)             18

upstream           r-3        8/(r-3)              8
</pre>
Those times are given as equal.


{{{18/(r+3)=8/(r-3)}}}
Solve.

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{{{9/(r+3)=4/(r-3)}}}


{{{4(r+3)=9(r-3)}}}


{{{4r+12=9r-27}}}


{{{12+27=5r}}}


{{{r=(12+27)/5}}}


{{{r=39/5}}}


{{{r=7&4/5}}}