"Are you asking your daughter?"
Translation:Ptáte se svojí dcery?
"Ptáš tvou dcery"- This is incorrect for two small reasons. You need the "se" after "ptáš" since it is a reflexive verb, and you used the accusative "tvou" instead of the genitive "tvé/tvojí". You could have also used "své/svojí" in this case, hence the discussion's translation.
"Zveš tvou dceru" - The verb zveš, from zvát, means something more like "to invite". So the suggestion makes some sense, perhaps in a context like asking your daughter to join you over the holidays.
Keep your chin up! This is definitely one of the tougher Duolingo courses I've tried. But I bet after enough practice, all the endings and quirks will eventually become second nature.
You cannot mix using the "ty" informal addressing of people (and hence the tvůj/tvá/tvé") and second person plural verbs (ptáte). It must be either:
Ptáte se své/svojí dcery? (better) / Ptáte se vaší dcery? (acceptable)
Ptáš se [své/svojí/tvé] dcery?
It is even possible to have
Ptáš se vaší dcery?
but there plural vaší is not the formal addressing, it is a real plural (the daughter of you two).