Question 980526
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X=number of pens; Y=number of pencils
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X+Y=108
Y=108-X Use this to substitute for Y below.
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rs7X+rs3Y=rs 564 Substitute for Y from above.
rs7X+rs3(108-X)=rs 564
rs7X+rs324-rs3X=rs 564 subtract rs 324 from each side.
rs4X=rs 240 Divide each side by rs 4.
X=60 ANSWER 1: The person bought 60 pens.
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Y=108-X
Y=108-60
Y=48 ANSWER 2: The person bought 48 pencils.
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CHECK:
A person spent rs 564 buying pens and pencils.
rs7X+rs3Y=rs 564
rs7(60)+rs3(48)=rs 564
rs 420+rs 144=rs 564
rs 564=rs564