the cost of one pen and two books together is rs70. the cost 3 pens and 9 books together is rs300. find the difference between cost of a book and a pen
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let the cost of one pen be X and the cost of one book be Y.
X + 2Y = 70
3X + 9Y = 300 => X + 3Y = 100
X + 2Y = 70
-X - 3Y = -100 ==> Y = 30 & X = 10
cost of one pen = rs10
cost of one book = rs30
done!!!
X + 2Y = 70
3X + 9Y = 300 => X + 3Y = 100
X + 2Y = 70
-X - 3Y = -100 ==> Y = 30 & X = 10
cost of one pen = rs10
cost of one book = rs30
done!!!
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