She bought 54 child tickets and 19 adult tickets.
Step-by-step explanation:
No. of tickets purchased = 73
Cost of tickets = $771
Cost of one child ticket = $9
Cost of one adult ticket = $15
Let,
Child ticket = x
Adult ticket = y
According to given statement;
x+y=73 Eqn 1
9x+15y=771 Eqn 2
Multiplying Eqn 1 by 9;
![9(x+y=73)\\9x+9y=657\ \ \ Eqn\ 3\\](https://tex.z-dn.net/?f=9%28x%2By%3D73%29%5C%5C9x%2B9y%3D657%5C%20%5C%20%5C%20Eqn%5C%203%5C%5C)
Subtracting Eqn 3 from Eqn 2;
![(9x+15y)-(9x+9y)=771-657\\9x+15y-9x-9y=114\\6y=114\\](https://tex.z-dn.net/?f=%289x%2B15y%29-%289x%2B9y%29%3D771-657%5C%5C9x%2B15y-9x-9y%3D114%5C%5C6y%3D114%5C%5C)
Dividing both sides by 6;
![\frac{6y}{6}=\frac{114}{6}\\y=19](https://tex.z-dn.net/?f=%5Cfrac%7B6y%7D%7B6%7D%3D%5Cfrac%7B114%7D%7B6%7D%5C%5Cy%3D19)
Putting y=19 in Eqn 1
![x+19=73\\x=73-19\\x=54\\](https://tex.z-dn.net/?f=x%2B19%3D73%5C%5Cx%3D73-19%5C%5Cx%3D54%5C%5C)
She bought 54 child tickets and 19 adult tickets.
Keywords: linear equations, subtraction
Learn more about linear equations at:
#LearnwithBrainly