"Yo no sé cuándo es el baile."
Translation:I don't know when the dance is.
I put I DON'T KNOW WHEN IS THE DANCE and its still marked wrong?? Isn't it the same????
No, in this type of sentence in English, the verb "to be" goes last: I don't know where the restaurant is, Do you know when the party is?, Can you tell me who her boss is?, We know who the winners are, We need to find out how the patients are, etc.
No: "I need to know: when is the dance?" Is fine. English finds sentences with two complete clauses to be perfectly acceptable. Further, there not only is no rule that "to be" must go at the end of a sentence in this sort of case, for some time the practice was frowned upon.