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Kelvin had some money. If he buys 3 books, he will have $12 left. If he buys 5

books, he will be short of $4. Find the cost of a book.

 Dec 29, 2021
 #1
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$12 + $4 = $16

5 - 3 = 2

$16 / 2 = $8

 Dec 29, 2021
 #2
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The cost of a book is $4. smiley

Guest Dec 29, 2021
 #3
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Kelvin had some money. If he buys 3 books, he will have $12 left. If he buys 5

books, he will be short of $4. Find the cost of a book.    

 

Let M stand for Kelvin's money, and let B stand for the price of a book.  

 

M – 3B = 12      (equation 1)  

M – 5B = –4      (equation 2)  

 

Subtract eq 2 from eq 1  

 

2B = 16  which means  B = 8  i.e., The cost of one book is $8. 

 

You can go on to determine that Kelvin started with $36 but the problem doesn't ask for that. 

.

 Dec 29, 2021

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