Question 1200264
Tortula to Cactus       r, 204 miles

Cactus to Dry Junc.     r+13, 308 miles

Total time, 6 hours


First part's time,  {{{204/r}}}
Second part's time, {{{308/(r+13)}}}


TIME SUM:  {{{204/r+308/(r+13)=6}}}-----------Solve for r.