"The man and the woman speak Swedish."
Translation:Mannen och kvinnan talar svenska.
Saying "De kan svenska" is much more commonly said in swedish than using "talar" or "pratar."
Yes, but it does not mean the same thing. Your sentence "de kan svenska" just means that they know how to speak Swedish, whereas the sentence here means either that OR that they speak Swedish as in what they're currently doing.
Both are correct, and both mean "I can speak Swedish," but saying "Jag talar svenska" is a lot more formal, more than for normal conversation.