Hi. Easier to visualize when drawing the route out.

KIV: Julie is faster by 4km/h.

Let meeting point be X (1okm from B).

Julie goes from A to X to B (at “4-hour” mark)  then back to X.

Ryan goes from A to X.

So, Julie travelled 20km (10km + 10km) more than Ryan when they met.

Recall: Difference in speed is 4km/h.

Time taken by Julie at meeting point X is 20/4=5hr (or “5-hour” mark)

from “4-hr” mark (at B) to “5-hr” mark (at meeting point X), time taken by Julie is 1hour. Distance travelled by her is 10km. So Julie’s speed is 10km/h.

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
u =1

Therefore Julie speed is 10u = 10km/hr ####