Question 843410
There's actually not enough information here.  Do these have to be whole numbers?  Is there a ratio between adult and child tickets, such as adult tickets cost twice as much?
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If they each cost the same, then the tickets are 85/11 or $7.73 each.
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But I doubt that's the answer.  There's not enough information for a formula, so we'll just use arbitrary numbers.
6 adult tickets at $10 = $65, leaving $20 for students tickets.  $20/5 = $4 each.
That's one possible solution.  Adult = $10; Student = $4.
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What if adult tickets are only $5?  Then 6*5=30, leaving the student tickets to total $55.  55/5 = $11 each.  Adult = $5 and student = $11.  That fits, but student tickets are usually discounted.
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Is there more information given?  Else, your instructor is likely looking for the $10/$4 scenario.