Directions:- Study the following information carefully to answer the question given below.
85 children went to an amusement park where they could ride on Roller-coaster, Giant wheel and Toy-train. 20 of them took all the three rides and 55 of them took at least two of three rides. Each ride costs Rs. 10 and total receipt of the amusement park from children was Rs. 1,450.
How many children took exactly one ride?