A car travels from B at a speed of 20 km/hr. The bus travel starts from A at a time of 6 A.M. There is a bus for every half an hour interval. The car starts at 12 noon. Each bus travels at a speed of 25 km/hr. Distance between A and B is 100 km. During its journey, The number of buses that the car encounter is ?
Note- Car travels from B to A and bus A to B
I assume the car is travelling from $B$ to $A$, although you don't say this. The first bus that the car meets (at $B$) left $A$ four hours earlier at 8am. The last bus that the car meets (at $B$) leaves five hours later at 5pm. Between 8am and 5pm inclusive, 19 buses leave.
Whether the first and last buses count is ambiguous ("During its journey..."). So you can make a case for 17. But the question (as you translated it, at least) is poorly worded.