Answer:
30 child tickets
Explanation:
Let the number of children in the theater on Friday be c
as given that the number of adults on Friday in the theater is 3 times that of number of children
Hence number of adults = 3c
Cost of adults ticket = 9.10
cost of child ticket = 6
total cost = 9.1(3c) + 6c = 999
hence
27.3c+6c=999
33.3c=999
dividing both sides by 33.3
c=30
Hence there were 30 children in theater on Friday