Answer:
The expression for the average number of tickets sold per school child is:
Step-by-step explanation:
The average number of tickets sold per school child is the weighted mean calculus between the number of tickets sold by these classes and the number of children in each classes.
This is the multiplication between the number of tickets sold by these classes and the number of children in each classes divided by the total weight(in this exercise, the total weight is the total number of school child).
So, the expression for the average number of tickets sold per school child is: