Expressing age

1. English expresses age using the adjective 'old'.
   How old are you.
   I am 15 years old.
2. In Russian, the person whose age is being told is in the dative case.
3. In expressing age Russian does not use the equivalent of the adjective old.
4. The age is followed by a word for year(s).
5. If the number of years ends in the numeral 1 (1, 21, 31...), use the word год:
   Ему 21 год. He is 21 years old.
6. If the number of years ends in the numerals 2-4 (2, 22,24, 33), use the word года:
   Ей 24 года. She is 24 years old.
7. If the number of years ends in any other numeral (55, 20), use the word лет:
   Ему 55 лет. He is 55 years old.
8. If the number of years ends in the numerals 5-9, 11-19, or 0, use the word лет:
   Мне 8 лет.
   Ей 13 лет.
   Тебе 29 лет.
   Ему 10 лет.
9. Anecdote:
   -Тебе сколько лет?
   -Пять. А тебе?
   -Не знаю.
   -Ты интересуешься девочками? (interested in girls)
   -Нет.
   -Значит тебе четыре года.