Greetings!
This would probably be the most accurate solution:
Mary buys: 10 adult tickets, and 4 child tickets.
10 adult tickets = 90 dollars
4 child tickets = 20 dollars
90 + 20 = 110 ~ 4 + 10 = 14
This might be just the perfect solution. Hope this helps... tell me if I am wrong!
~Lauv