Question 248836
Use: x+y=total items
So, x+y=89
y=89-x
and 
Use: ax+by=(total)(ratio)
So, 4.10x+2.70y=331.30
4.10x+2.70(89-x)=331.30[substitute y=89-x)
4.10x+240.30-2.70x=331.30
4.10x-2.70x=331.30-240.30
1.40x=91
x=91/1.40
x=65 adult tickes 
65+y=89
so,
y=89-65=24 children tickets sold