6 . A car can cover a certain distance in 3$1\over 3$ hours. If the speed is increased by 6 km/hr, then it would take $1\over 3$ hours less time to cover the same distance. Find the initial speed of the car.
8 . A can do a certain work in the same time in which B and C together can do it. If A and B together can do the same work in 25 days and C alone can do it in 75 days then in how many days B can do the work ?