How do I hyphenate an age, such as 23 year old or twenty three year old? Is it 23 year-old and twenty-three year-old?
Do not add a hyphen between "year" and "old." If you are writing out numbers (such as fifty-second or thirty-eight), put a hyphen between the words if the number is less than a hundred.
one hundred and nine (109)
two hundred and thirty-five (235- this number is greater than a hundred, but the hyphen should still be added to the thirty-five)