Explanation:
the average of something is always
(the total sum of that something) / (number of observation units)
Part A
the total sum for May is 2356.
the number of observation units (days in May) : 31
so, the average daily number of parking tickets in May was
2356/31 = 76
Part B
the total sum for May : 2356.
the total sum for June : 1560.
number of observation units (days) in May : 31
number of observation units in June : 30
the average daily number in May : 2356/31 = 76
the average daily number in June : 1560/30 = 52
the difference in the daily numbers in May and June :
76 - 52 = 24