Let's just make 15 students a group. how many groups are there if there r 135 student? 135/15 = 9 groups. so if each group have 4 adults just multiply 9 by 4, therefore there will be 36.adults.
According to the data given in the question, between 9 and 10 AM, 220 passengers have checked in which means that the check-in rate is 3.6 passengers per minute. If the average number of passengers waiting for check-in is 32 and if we assume that the check-in rate is constant throughout the day, then the average passenger had to wait in line for 3.6 minutes.