At the movie theatre, child admission is $5.50 and adult admission is $8.60. On Thursday, twice as many adult tickets as child tickets were sold, for a total sales of $726.40. How many child tickets were sold that day?

Let child admissions be x and adult admissions be y. We can then use the information given to form a system of equations and solve that system.

The first equation is based on the information about the money made.

5.50x+8.60y=726.40

The second equation is based on the fact that twice as many adult tickets as child tickets were sold.

y = 2x

Since we have an equation equal to one of the variables, substitution will be the easiest way to solve this system. This is when we replace the variable of an equation with its value in the other.

5.50x+8.60y=726.40

5.50x+8.60 (2x) = 726.40

5.50x+17.2x = 726.40

22.7x = 726.40

x = 32

The number of children tickets sold was 32.

Extra:

To find the number of adult tickets can be found by plugging in the known value we found and solving for the other unknown.

y = 2x

y = 2 (32)

y = 64

The number of adult tickets sold was 64.