It's a way of asking someone their age, specifically if they are twelve years old. It's a bit informal and could be used between friends or family.
The phrase literally translates to "And you, twelve years." However, in English, we don't usually say "twelve years" to refer to a person's age.
Here are some ways the phrase might be used in conversation:
* "J'ai dix ans. Et toi, douze ans ?" (I am ten years old. And you, twelve years old?)
* "On est tous dans la même classe, mais toi, tu as douze ans ?" (We're all in the same class, but are you twelve years old?)
Let me know if you'd like to explore other French phrases or have any other questions!