Answer:
Is there a map of the town? It doesn't make sense without coridnates or street lengths. If it was a straight isosilese triangles the return time is 3:36pm. This answer doesn't make sense if there is a map.
Explanation:
Side a is 12km Side b 15 km Side c 19.21 km.
9am depearture
11am 12km away rest
11:30am starts at 10 km/h
1:00 pm reaches town
2:00pm done lunch
3:36 pm return home.