Why do this problem?
is one to use when relating time and distance and especially when looking at timetables and the $24$ hour clock. Timetables are tricky things and they sometimes need careful thinking to make sense of them. There are many conventions involved in their presentation and learners may need help in finding
the meanings in them.
Have you drawn a diagram of the buses on the road from A to B?
How many buses are on the road at $0600$?
How many buses are on the road at $0620$, $0640$, $0700$ and so on?
Do you understand how the $24$ hour clock works?
Learners could find out bus times from a local timetable and even make up their own problem about them.
Suggest starting by drawing a picture all the coaches on the road at various times.