Question 1013187
<pre>
            rate        time         distance
OUT          4           x            d
BACK         2           y            d
Total                    6           2d
</pre>


{{{system(4x=d,2y=d,x+y=6)}}}-------three equations in three unknown variables, x, y, d.


To begin handling the system,  {{{y=6-x}}};
{{{system(4x=d,2(6-x)=d)}}}
...and maybe you can do the rest.



---
d=8