Answer: 76 child tickets were sold that day.
Explanation:
You need to set up a system of equations.
Let be "c" the number of child tickets sold that Wednesday and "a" the number of adult tickets sold that Wednesday.
Then:
![\left \{ {{a+c=173} \atop {9.40a+5.70c=1345.0}} \right.](https://img.qammunity.org/2020/formulas/mathematics/high-school/qdrjy9005m9uvqxird71mfqotat3nm81zb.png)
Using the Method of Elimination, you can multiply the first equation by -9.40, then add both equations and finally solve for "c":
![\left \{ {{-9.40a-9.40c=-1626.2} \atop {9.40a+5.70=1345.0}} \right.\\..................................\\-3.7c=-281.2\\\\c=(-281.2)/(-3.7)\\\\c=76](https://img.qammunity.org/2020/formulas/mathematics/high-school/pqi6i3mxx7qtc7884rmjyanlrfcd43ynp6.png)