The question is incomplete. The complete question is :
A man travels by a car from town A to town B, a total distance of 100 km at an average speed of x km/h. he finds that the time for the journey would be shorter by 25 minutes if he increases his average speed by 12km/h. Find x ?
Solution :
It is given the that the distance between town A and B is = 100 km
His initial average speed is = x km/h
His increased average speed is = 12 km/h
Time is shortened by = 25 minutes
So according to the question,
x-12 = 2500
x = 2512