Question 721078
University Theater sold 445 tickets for a play. Tickets cost $20 per adult and $12 per senior citizen. If total receipts were $6156, how many senior citizen tickets were sold? 
a=adults
s=seniors 
a+s=445
20a+12s=6156
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20a+12s = 6156
12a+12s = 12*445
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Subtract and solve for "a":
8a = 816
a = 102 (# of adult tickets sold)
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Solve for "s":
a + s = 445
102 + s = 445
s = 343 (# of student tickets sold)
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Cheers,
Stan H.