Answer: an adult ticket costs $9
A child's ticket costs $15
Step-by-step explanation:
Let x represent the price of an adult ticket.
Let y represent the price of a child ticket.
On the first day of ticket sales the school sold 6 adult tickets and 6 child tickets for a total of $144. This means that
6x + 6y = 144- - - - - - - - - - - - -1
The school took in $126 on the second day by selling 4 adult tickets and 6 child tickets. It means that
4x + 6y = 126 - - - - - - - - - - - - -2
Subtracting equation 2 from equation 1, it becomes
2x = 18
x = 18/2
x = 9
Substituting x = 9 into equation 2, it becomes
4 × 9 + 6y = 126
36 + 6y = 126
6y = 126 - 36
6y = 90
y = 90/6
y = 15
