含数词的短语
1) at the age of：在……岁时
He went abroad at the age of 18.
2) in one’s + 序数词复数 在某人几十多岁的时候
He started a company in his fifties.
3) 带有数词的名词作定语的表达
a seven-year-old boy a hundred-meter race
a ten-minute walk = 10 minutes’ walk
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