Given:
Cost of adult's ticket = $15
Cost of children's ticket = $8
Total tickets = 725
Total sales = $8775
To find:
The number of each type of ticket were sold.
Solution:
Let x be the number of adult tickets and y be the number of children's ticket.
Total tickets :
...(i)
Total sales :
...(ii)
Multiply equation (i) by 15.
...(iii)
Subtract (iii) from (ii),
![15x+18y-15x-15y=8775-10875](https://img.qammunity.org/2021/formulas/mathematics/high-school/xnqo5gekdbmy2q95733puhbx4aogqyxmue.png)
![3x=-2100](https://img.qammunity.org/2021/formulas/mathematics/high-school/9zughmj2qgip44h5xt2uaadkje3lrzbw5w.png)
![x=-700](https://img.qammunity.org/2021/formulas/mathematics/high-school/nt1lfm9rn7c6mkdqsimzgrcugzej5hfkp7.png)
Putting x=-700 in (i), we get
![-700+y=725](https://img.qammunity.org/2021/formulas/mathematics/high-school/tecoph8uqxiodzdhwvn0bmfx6jtyhjthq8.png)
![y=725+700](https://img.qammunity.org/2021/formulas/mathematics/high-school/1tg643kqw95hm2pqncefrvssukuketm3ml.png)
![y=1425](https://img.qammunity.org/2021/formulas/mathematics/high-school/k5cymfgg5h4lnlibbra3mom1eskgbaohxj.png)
Therefore, the number of adult tickets is -700 and number of child tickets is 1425.
Note: The number of tickets cannot be negative. So, there must be some error in the question.