Answer:
53
Step-by-step explanation:
Let x be the number of children tickets sold and y be the number of adult tickets sold. Then
x+y=128.
The cost of x children tickets is $5.10x and the cost of y adult tickets is $9.70y, so
5.10x+9.70y =896.60.
From the first equation,
x=128-y,
then
[tex]5.10(128-y)+9.70y=896.60,\\ \\652.80-5.10y+9.70y=896.60,\\ \\4.60y=243.8,\\ \\y=53.[/tex]
53 adult tickets were sold.