9514 1404 393
Answer:
250
Explanation:
Let 'a' represent the number of adult tickets.
a +(a -73) = 427
2a = 500 . . . . . add 73
a = 250 . . . . . . divide by 2
250 adult tickets were sold.
_____
Additional comment
I call this a "sum and difference problem" because we are given the total of two values and the difference between them. As you can see here, the larger of the two values is the average of the given numbers, their sum divided by 2. This is the generic solution to such a problem: the larger number is the average of the given sum and difference.