"Why do you use all three sinks for the same?"
Translation:Hvorfor bruger du alle tre vaske til det samme?
No, not literally, but in this context, "til det samme" means "for the same purpose".
Then it should say that so we're able to translate it. As it is, the English sentence is unnatural.
I totally agree, but the original question was in Danish to English (in an earlier lesson). In other words, the Danish version is correct, but the English translation is incomplete.