Sam buys 2 adult tickets and 3 child tickets for $44.40.John buys 3 adult tickets and 6 child tickets for $78.How much does a child ticket and adult ticket cost?
2a+3c = 44.40
3a+6c = 78.00
That's the same as
2a+3c = 44.40
a+2c = 26.00
subtract and you get
a+c = 18.40
Note that we don't actually have to find the price of the individual tickets.