Answer:
<h2>(170;120;60).</h2>
Step-by-step explanation:
<h3>We know that:</h3>
Capacity of the theater: 350 people.
Adults is half the students.
Children's cost: $4.50
Student's cost: $7.50
Adults' cost: $12.50
Total Sales: $2415
We are gonna call <em>x </em>the children, <em>y </em>the students and <em>z </em>the adults:
So, the equation to express the capacity of the theater would be:
![x+y+z=350](https://tex.z-dn.net/?f=x%2By%2Bz%3D350)
But,
(adults are have students)
So, the expression would be: ![x+y+\frac{y}{2} =350](https://tex.z-dn.net/?f=x%2By%2B%5Cfrac%7By%7D%7B2%7D%20%3D350)
<h3>Solving <em>y's </em>and Isolating <em>x </em>: </h3>
![x+\frac{3y}{2} =350\\x=350-\frac{3y}{2}](https://tex.z-dn.net/?f=x%2B%5Cfrac%7B3y%7D%7B2%7D%20%3D350%5C%5Cx%3D350-%5Cfrac%7B3y%7D%7B2%7D)
<h3>Now, we need a expression for costs. We have:</h3>
![4.50x+7.50y+12.50z=2415](https://tex.z-dn.net/?f=4.50x%2B7.50y%2B12.50z%3D2415)
<h3>Replacing the <em>x </em>and <em>z </em>equation:</h3>
![4.50(350-\frac{3y}{2} )+7.50y+12.50\frac{y}{2}=2415](https://tex.z-dn.net/?f=4.50%28350-%5Cfrac%7B3y%7D%7B2%7D%20%29%2B7.50y%2B12.50%5Cfrac%7By%7D%7B2%7D%3D2415)
<h3>Now, we solve for <em>y</em>:</h3>
![1575-6.75y+7.50y+6.25y=2415\\07y=2415-1575\\7y=840\\y=\frac{840}{7} =120](https://tex.z-dn.net/?f=1575-6.75y%2B7.50y%2B6.25y%3D2415%5C%5C07y%3D2415-1575%5C%5C7y%3D840%5C%5Cy%3D%5Cfrac%7B840%7D%7B7%7D%20%3D120)
<h3>But, we know that adults are half as many students, so:</h3>
![z=\frac{y}{2}=\frac{120}{2} =60](https://tex.z-dn.net/?f=z%3D%5Cfrac%7By%7D%7B2%7D%3D%5Cfrac%7B120%7D%7B2%7D%20%3D60)
<h3>Lastly,</h3>
![x+y+z=350\\x+120+60=350\\x=350-120-60\\x=170](https://tex.z-dn.net/?f=x%2By%2Bz%3D350%5C%5Cx%2B120%2B60%3D350%5C%5Cx%3D350-120-60%5C%5Cx%3D170)
<em>Therefore, there are 170 children, 120 students and 60 adults. Expressing the results as an ordered triple would be (170;120;60)</em>