Question 766839
h is total time
d is total distance

ROAD______________speed_______time___________distance
Highway___________60_________(3/4)h_________(5/6)d
NonHighway________(___)______(1/4)h_________(1/6)d


ROAD______________speed_______time___________distance
Highway___________60_________(3/4)h_________(5/6)d
NonHighway________(r)______(1/4)h_________(1/6)d


Try making two equations using rate times time equals distance:
{{{60*(3/4)h=(5/6)d}}} and {{{r(1/4)h=(1/6)d}}}; this last equation gives an expression for unknown r.
{{{(d/h)(4)(1/6)=r}}}
{{{r=(2/3)(d/h)}}}
But we still have three variables and two equations, just one is rearranged.  


This seems an open-ended problem.  Use the highway equation to eliminate either the h or the d in the r equation.  You might want to pick an arbitrary value for h or d.

Work with the highway equation....
{{{d=54*h}}}
So you can form the equation {{{r=(2/3)(54h/h)}}}
{{{r=(2/3)*54}}}
{{{r=36}}}
No longer seems so open-ended.  Solution method felt strange, but result is very clear.

With that result r=36 mph, you can evaluate possible averages of highway and nonhighway speeds.