Let the distance from the village to the post-office be d km.
The distance from village to post-office is the same as the distance from post-office back to village.
Speed going to post-office = 25 km/hr
Speed walking back = 4 km/hr
Total time for both trips = 5 hours 48 minutes
Converting the total time to hours:
5 hours 48 minutes = 5+6048 hours
=5+54
=5+0.8
=5.8 hours
Using Time = Distance ÷ Speed:
Time to go to post-office = 25d hours
Time to walk back = 4d hours
The total time is 5.8 hours:
25d+4d=5.8
The LCM of 25 and 4 is 100.
1004d+10025d=5.8
10029d=5.8
29d=580
d=20
The distance of the post-office from the village is 20 km.