Not addition, since

and 0 doesn't belong to the set.
Not subtraction, since

.
It is closed under multiplication. The set appears to contain all non-zero multiples of 3.
Not division, since dividing some of the numbers results in rationals which do not belong to the set.
What other operations are you supposed to consider?
The cost of one bus ride is 2% of the initial value of pass.
Step-by-step explanation:
Initial value of pass = $90
Cost of one ride = $1.80
Cost percent of one ride = 

The cost of one bus ride is 2% of the initial value of pass.
Keywords: percentage, division
Learn more about division at:
#LearnwithBrainly
The number of people who like to fish AND swim is 8 people
The number of people who ONLY like to fish is 11 people
The number of people who ONLY like to swim is 23 people
The number of people who DO NOT like to fish is 23 people
The number of people who DO NOT like to swim is 11 people
The number of people who DO NOT like EITHER to fish or to swim is 6 people
The total of people is 11+8+23+6=48
the answer is 15 because 12 is 80% of 15