What does "cuántos años tienes" mean?
¿Cuántos años tienes?
...would be better - especially the tilde over the ñ, because anos (no tilde) means anuses.
The question was originally asking how many anuses you have...
Accents, or lack of them, can completely change the meaning of words and sentences, so it's best to learn them along with the letters.
In Spanish, asking someone their age is more literally translated "How many years do you have?" You would answer "I have....years.
It is just one of those things that can not be translated word for word from English to Spanish.