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Equations:
Quantity Eq.::: x + y = 480
Value Eq.::::: 5x +8y = 2895
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Multiply thru the Quantity equation by 5
5x + 5y = 5*480
5x + 8y = 2895
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Subtract the 1st from the 2nd:
3y = 495
y = 165 (# of non-student tickets sold)
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Since x+y = 480, x = 480-165 = 315 (# of student tickets sold)