I think I got it.......
total = $90
7 adults, 12 children
Let x = amount of adult's ticket ---> 7x because there is 7 adults
2/3 x = amount of child's ticket ---> 12(2/3x) because child ticket is 2/3 of adult ticket and there is 12 children
7x + 12(2/3x) = 90
7x + 8x = 90
15x = 90
x = 90/15
x = $ 6 <--- price of adult ticket
2/3(6) = 12/3 = $ 4 <--- price of child ticket
Check:
7(6) = $42
people * price = amount
12(4) = $48
people * price = amount
$42 + $48 = $90
hope this helps :)
