A policeman starts to chase a thief. When the thief goes 10 steps the policeman moves 8 steps. 5 steps of the policeman is equal to 7 steps of the thief. The ratio of the speeds of the policeman and the thief is

5 steps of Policeman = 7 steps of a thief

=> 1 step of Policeman = 7/5 steps of thief

=> 8 Steps of Policeman = 8 x 7/5 steps of thief = 56/5 steps of thief

The ratio of speeds of policeman and thief = ratio of distance covered by policeman and thief in a same time

=> In same time policeman moves 8 steps and thief moves 10 steps

=> 56/5 : 10 (because as we calculated earlier 8 steps of policeman = 56/5 steps of thief)

=> 56 : 50 = 28 : 25