I've known "umieć" as being a verb used for 'knowing how' to do something. Would it not be better to have it as "to know how to" as opposed to "to be able to", as currently it's a bit too close to "móc" to notice the difference. (Please tell me otherwise if I'm mistaken.)
Yes, IMO the default sentece should be: Why don't you know how to cook. Or at least Why can't you cook.
In the Android app the answer is indeed given as "Why can't you cook?", which is, I think, something of a first: I can't remember ever having seen an English contracted form used in a Duo answer before. Things are looking up.
In English the sentence 'Why can't you cook?' is ambiguous and can mean either 'Why don't you know how to cook?' or 'Why are you unable to cook?' (e.g. because both your arms are broken). Normally when people say 'I can't cook' they mean the former.
The translation now appears to be "can" rather than "able to". So, referring to your "know how to" point, when we say something like "I can swim", nine times out of ten we are talking about general ability: i.e. that we know how to do something, and I think it's rather more common to use "can" than "know how to" in this context.
In some languages this use of "can" is translated wih a verb for know, e.g. "Je sais nager" (fr). Similarly the standard Polish translation of "can" in this meaning apears to be with "umieć". From Collins Słownik:
"I can swim - umiem pływać"
So for me, while "Why don't you know how to cook?" is fine, "Why can't you cook?" is possibly more natural here, and that more importantly, Duo are right to show this relationship between "can" and "umieć".
(Corrected - thanks to 880201)
I agree - the English 'can' is ambigous. Umiec is 'able to' in the dictionary not can.
I don't know what dictionary you're referring to but this is from the PWN/Oxford Wielki Słownik:
"nie umiem tańczyć/pływać - I can't dance /swim"
When talking of ability, "be able to" has exactly the same meaning as "can", and we can often use either. The only difference is that when there's a choice "able to" sounds a bit formal so we usually prefer "can/could". And that sometimes "can/could" is not possible and we can only use "be able to":
"He can (is able to) to do it tomorrow"
"He should be able to do it tomorrow"
"Why can't you cook?" (Duo's Android app answer), is fine here, as would be "Why don't you know how to cook?"
= Correct solutions: = Why don't you know how to you cook?, Why can't you cook? Why in the first variant the word "you" is repeated 2 times?
Someone (most probably me) wasn't careful enough when editing the answers... that's obviously an absurd answer. Fixed now, thanks a lot for reporting.
You used the wrong word. Why don't you know how to cook?
Why you don't know how to cook is wrong ???
Well I don't think so!!!!
Yes, "Why you don't know how to cook" is wrong. That's not the correct word order of an English sentence.
Yes, I fell into that trap too and became confused with ;able
Yes, I too became confused with the English 'can' and 'able'. I know that umieć is to know how. So when I wrote 'Why are you unable to cook' Duo found it unacceptable. English words are so slippery in their meanings!