We know that
• 9 tickets cost $54.
,
• Adult tickets cost $8.
,
• Child ticket costs $3.50.
Let's call x adult tickets and y child tickets.
Using the given information, we can define the following.
![x+y=9](https://img.qammunity.org/2023/formulas/mathematics/high-school/dr61unb4wnkks46ggqnac4pvgknxg7vewb.png)
Because Jose bought 9 tickets in total.
Then, we express another equation.
![8x+3.50y=54](https://img.qammunity.org/2023/formulas/mathematics/college/p4qv1g3m1zdy9t752b13ggrf0ba6us6kbu.png)
This equation represents the costs.
Let's isolate y in the first equation.
![y=9-x](https://img.qammunity.org/2023/formulas/mathematics/college/u31d4c05vhavw5y6tks98ch0cg2ikcdv2e.png)
Then, we replace this last expression in the second equation.
![8x+3.50(9-x)=54](https://img.qammunity.org/2023/formulas/mathematics/college/t37pjbzs6rzdgzlxmac4uqe5s0aorrx6v3.png)
We solve for x.
![\begin{gathered} 8x+31.50-3.50x=54 \\ 4.50x=54-31.50 \\ 4.50x=22.50 \\ x=(22.50)/(4.50) \\ x=5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/3at6p2zzef7n1aq2xxaxd76a80dfsfnqvn.png)
Therefore, Jose bought 5 adult tickets.