Please read the below given text for solving the question In a school Eighty Five students went to circus where they could ride on merry “go-round roller coaster and Ferris wheel .It was known that 20 of them have took all three rides and 55 of them have taken at least two of the three rides. Each ride cost Rs.1 and the total receipt of the circus was Rs.145.

20 students * 3 rides = Rs. 60
(55-20=)35 students * 2 rides = Rs. 70
60 + 70 = Rs. 130
So, Rs. (145 - 130 = ) 15 are left for the other (85 - 55 = ) 30 students . so only 15 of them can take a ride and rest 15 will be left out.
145 rides were taken. 20 of them took all three, i.e. Rs. 60 were spent, so 145-60= Rs. 85 are left for the others. Total students were 85, so rest were 65. out of these 65, 35 students ride at least 2 rides and other 30 of them 15 will take one ride other 15 is left