"What is the minimum age?"

Translation: Qual é a idade mínima?

[marinkydink]

Is "O que é a idade mínima?" incorrect?

[Paulenrique]

If you use o que you ask about the meaning of the expression "a idade mínima". If you translate "qual" then it means what the minimum age is.

[moostela]

I was always cofused about the usage of "o que" vs. "qual". So is it everytime like this or are there other situations/meanings to keep in mind, if I have to decide weather to use "o que" or "qual"?

[Paulenrique]

http://www.duolingo.com/comment/951610

[KrisKalis]

Shouldn't it be like other age sentences - 'How much is the minimum age'? Or is that specific to numbers?