At the city museum, child admission is $5.60 and adult admission is $9.20. On Sunday, 145 tickets were sold for a total sales of $1020.80. How many child tickets were sold that day?

Let x be the number of child admission tickets sold:

Child's ticket = x

There is a total of 145 tickets sold:

Adult = 145 - x

Total sales is $1020.80:

5.6x + 9.2 (145 - x) = 1020.8

Solve for x:

5.6x + 9.2 (145 - x) = 1020.8

5.6x + 1334 - 9.2x = 1020.8

3.6x = 313.2

x = 313.2 : 3.6

x = 87

Answer: Number of child's ticket = 87

Number of children (x) is 87

number of adults (y) is 58

and this is the work (it's a linear equation system)

hope you understand it

good luck