Can we say "three-year" instead of saying "three years"?

The phrase #1 is grammatically incorrrect because when you use the word "old" to refer to the age of a person or thing, it's a postpositive adjective. ... When you combine the words in the phrase "three years old" by hyphenating them to make it an adjective or a noun, you must use the singular noun (year).

person against person: the hunger games bookteens were sent to fight against each other. they were sent in groups of two's. but could only be one winner. this conflict gave me a emotion of sadness. it made me feel bad for the kids that was sent there.  

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one time i was sleeping on a bench outside of walgreens and someone offered me money because they thought i was homeless

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