"These are the ten new states."
Translation:Acestea sunt cele zece state noi.
- These are ten new states. = Acestea sunt zece state noi.
- These are the ten new states. = Acestea sunt cele zece state noi.
You must NOT use "de" for: 0-19, 101-119, 201-219, 301-319, . . . , and so on.
You should use "de" for: 20-100, 120-200, 220-300, . . . , and so on.
Oh, and BTW, when you write the number as a numeral (using digits instead of words), you can omit the "de". But only in writing! When you read it aloud, you say the "de" according to the rules I mentioned.