An aeroplane flying with a wind of 30 km/h takes 40 minutes less to fly 3600 km , then what it would have taken to fly against the same wind. Find the plane's speed of flying in still air.

A school bus transported an excursion party to a picnic spot 150 km away. While returning , it was raining and the bus had to reduce its speed by 5 km/h , and it took one hour longer to make the return trip. Find the time taken to return.

₹480 is divided equally among 'x' children. If the number of children were 20 more, then each would have got ₹12 less . Find 'x'.