<PRE><B>Question 864631</B>
Use basic uniform rates concept, RT=D, and setup a data table to help relate all the data.


_________________speed__________time__________distance
FirstPart________r______________{{{51/r}}}_____________51
Return___________r-6____________{{{51/(r-6)}}}_________51
TOTAL____________________________15


Solve for r in the equation for time sum, {{{highlight_green(51/r+51/(r-6)=15)}}}.
This will be simpler as {{{highlight_green(17/r+17/(r-6)=5)}}}.</PRE>