I'm not sure what you are asking. However, the punctuation of the second one is: He is a 40-year-old gentleman.
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AnonymousWhat is the grammar of the old in [ He is 40 years old. ] ?It's an adjective that describes the kind of measurement being done. Such adjectives occur after the numerical measurement itself, which consists of a number and a unit of measurement. Here are some of the more commonly used patterns of this kind: