Final answer:
To find the number of child tickets sold, we can solve a system of equations. Using the given information, we set up two equations and solve for the unknowns. In this case, 54 child tickets were sold that day.
Step-by-step explanation:
To find the number of child tickets sold, we can set up a system of equations based on the given information. Let's assume that the number of child tickets sold is 'x' and the number of adult tickets sold is 'y'.
From the problem, we know that the cost of a child ticket is $5.10 and the cost of an adult ticket is $9.10. The total sales for 129 tickets is $957.90.
So, we have the following equations:
x + y = 129 (equation 1, representing the total number of tickets sold)
5.10x + 9.10y = 957.90 (equation 2, representing the total sales)
We can solve this system of equations using substitution or elimination method. Let's use elimination.
Multiplying equation 1 by 5.10 to get rid of the decimals:
5.10x + 5.10y = 658.20 (equation 3)
Subtracting equation 3 from equation 2:
9.10y - 5.10y = 957.90 - 658.20
4y = 299.70
y = 74.925
Rounding y to the nearest whole number (as we can't have a fraction of a ticket), we get:
y = 75
Substituting the value of y into equation 1:
x + 75 = 129
x = 54
Therefore, 54 child tickets were sold that day.