Question 704236
The description tells nothing about how this person distributes his time between the swimming and the running.  We can find an interval of distance which might be possible for the 3 hour time period.


The person will swim, but not for all three hours.  The lowest distance possible must be more than (6 km/hour)*3 hours=18 km.


The person will run, but not for all three hours.  The highest distance possible must be less than (18 km/hour)*3 hours=54 km.


Using x for distance, {{{18<x<54}}}.  Does this exercise have more information?