Answer:
8.50(c+a)
Explanation:
Here,
Total number of children who bought tickets = c,
Total number of adults who bought tickets = a
Thus, the total number of people = children + adults
= c + a
Now, the cost of ticket for each person = $ 8.50,
So, the total cost of the tickets bought by 'c+a' persons = 8.50(c+a)
Which is the required expression.