At the movie theatre, child admission is $6.40 and adult admission is $9.80 . on monday, 154 tickets were sold for a total sales of $1291.60 . how many child tickets were sold that day?

Let x be the child ticket and y be the y adult ticket.

so x+ y =154
6.40 x + 9.80 y = 1291.60
substitute y= (154-x) in the second equation. 6.40x+9.80(154-x) = 1291.60
6.40x-9.80x=1291.60- 1509.20
-3.40 x =-217.60
x=64
64 child tickets were sold .