A car drives downhill with the speed of 90 m/h. On a level road, the same car goes 72 m/h, and uphill it goes "only" 60 m/h.
It takes this car 5 hours to go from town A to town B. The return trip only takes 4 hours.
Find the distance between the two towns.
(In reply to Alternate approach
not like anyone will ever go this far back in the posts but,
an even more simplified version. Realize that 90/(hill) = 60/(hill) - 1. (well in my units anyways - 90 and 60 are the mph speeds, hill is the length of the graded section in miles, and 1 is the time difference in hours). This will let you calculate the length of the hill, from which point its pretty easy to finish.