Answer: 30 children tickets and 80 adult tickets were sold.
Explanation:
Let x represent the number of children tickets that were sold.
Let y represent the number of adult tickets that were sold.
A total of 110 tickets were sold. It means that
x + y = 110
The movie theater charges $8 for children tickets and $12 for adult tickets. The total sales from the tickets was $1200. It means that
8x + 12y = 1200- - - - - - - - - 1
Substituting x = 110 - y into equation 1, it becomes
8(110 - y) + 12y = 1200
880 - 8y + 12y = 1200
- 8y + 12y = 1200 - 880
4y = 320
y = 320/4
y = 80
x = 110 - y = 110 - 80
x = 30