Answer:
8 children tickets 10 adult tickets
Explanation:
The total amount should be $ 320 not 1,320 because if you divide that amount into 18 tickets it will be an average of $73.333 per ticket
A= adults C= children
A+C =18
C= 18-A
20A + 15(18-A) = 320
20A +270 -15A = 320
5A = 50
A= 10
10 adults 8 children
10x$20 =$ 200 8x$15 =$ 120
$200+$120 =$ 320