Question 1152023
d, the same distance both ways
<pre>
                  SPEED         TIME       DISTANCE
Down to Lake       r             4           d
Up to Return       r-4           6           d
</pre>
{{{(r)(4)=(r-4)(6)}}}


{{{4r=6(r-4)}}}

{{{4r=6r-24}}}

{{{2r=3r-12}}}

{{{r=12}}}