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.
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.
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