Relative speed = 4km/h.
After 4 hrs and when Julie just reached Town B, She had opened a gap of 4km/h X 4hr = 16km.
Now she turns back, facing Ryan. The gap between them is 16km.
From the statement,’she met Ryan who was 10km awayd from Town B”, says Ryan travelled 6km, and Julie travelled 10km to the meetup point.
Speed is proportional to distance travelled,
therefore speed ratio of Julie : Ryan is 10: 6
We know Julie is 4 km/h faster,
so 10u – 6u = 4km/h
Therefore Julie speed is 10u = 10km/hr ####