Out of curiosity, the reason we use лет here is because сколько always expects genitive plural, right? And it has nothing to do with the expected answer?
So would we say, for example, «сколько у тебя кошек?»
I've had a problem pronouncing Тринадцать. Tips, or is this a common problem with everyone?
I have the same problem, with all the -надцать numbers. Maybe I'm doing it wrong, but given how much leeway it gives me with other words, I'm thinking software issue.
When talking about age, dative is used.