Question 1005264
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C=number of couples; S=number of singles
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2C+S=59
S=59-2C
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P400C+P250S=P12150
P400C+P250(59-2C)=P12150
P400C+P14750-P500C=P12150
-P100C=-P2600
C=26 
ANSWER 1: There were 26 couples.
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S=59-2C
S=59-2(26)
S=59-52
S=7
ANSWER 2: There were 7 single parents.
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CHECK:
P400C+P250S=P12150
P400(26)+P250(7)=P12150
P10400+P1750=P12150
P12150=P12150
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