24 child tickets were sold that day.
Explanation
Lets assume, the number of child tickets sold is [tex]x[/tex]
As there are three times as many adult tickets as child tickets were sold, so the number of adult tickets will be [tex]3x[/tex]
Cost of each child ticket is $6.20 and cost of each adult ticket is $9.80
So, the total cost of x child tickets = $ 6.20x
and the total cost of 3x adult tickets = $9.80× 3x = $29.40x
Total amount of sales is given as $854.40 , so the equation will be...
[tex]6.20x+29.40x=854.40\\ \\ 35.60x=854.40\\ \\ x= \frac{854.40}{35.60}=24[/tex]
So, 24 child tickets were sold that day.
