Answer
39 child tickets were sold that day
Explanation
Variables
• x: child tickets sold
,
• y: adult tickets sold
Given that four times as many adult tickets as child tickets were sold, then:
![y=4x](https://img.qammunity.org/2023/formulas/mathematics/high-school/6yhq5l9ez0rs3whhqxkdo7mhfdidpcy3mr.png)
If 1 child ticket cost $5.70, then x child tickets will cost 5.7x dollars.
If 1 adult ticket cost $9.20, then y adult tickets will cost 9.2y dollars.
Given that the theater sold tickets for $1657.50, then:
![5.7x+9.2y=1657.5](https://img.qammunity.org/2023/formulas/mathematics/college/3uknqijus08lvbxggarcshxkhvmjuw255s.png)
Substituting the first equation into the second one and solving for x:
![\begin{gathered} 5.7x+9.2(4x)=1,657.5 \\ 5.7x+36.8x=1,657.5 \\ 42.5x=1,657.5 \\ (42.5x)/(42.5)=(1,657.5)/(42.5) \\ x=39 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/pv9qqvwgxv6sadbcsnhfdvrubjo3gkxzm1.png)