Answer: 96 adult tickets were sold that day.
Explanation:
Let x represent the number of children tickets that were sold at the movie theatre.
Let y represent the number of adult tickets that were sold at the movie theatre.
A total of 163 tickets were sold on Tuesday. This means that
x + y = 163
child admission is $5.70 and adult admission is $9.00. The total sales made on Tuesday was $1245.90. It means that
5.7x + 9y = 1245.90 - - - - - - - - 1
Substituting x = 163 - y into equation 1, it becomes
5.7(163 - y) + 9y = 1245.90
929.1 - 5.7y + 9y = 1245.90
- 5.7y + 9y = 1245.90 - 929.1
3.3y = 316.8
y = 316.8/3.3
y = 96
x = 163 - y = 163 - 96
x = 67