Problem : Two hikers, Call them Carl and David started to walk at 12pm (noon) along the same path but in opposite directions. Let's assume Carl walked from Point A to point B and David did the opposite, walked from Point B to Point A. Both of them have different constant speed. They pass each other at a point at 1500 hours. Carl arrived at Point B , 2.5 hours before David arrived at point A. When did David arrive at point A? Attempt: Carl Case 1) Xf = Xi + ViT assuming that his initial point Xi = 0 makes David's Xf = 0 as well. Xf = 0 + 3Vi. this Xf is the meeting point, therefore they have been walking for 3 hours, hence the 3Vi. Then I got stuck.. Thanks in advance !