"Hola, ¿qué tal estás?"
Translation:Hi, how are you?
Both "¿qué tal?" and "¿qué tal estás?" are correct. "¿que tal?" is more of a general "how's it going?" "¿que tal estás?" is more specific, as in "how are you?" "¿que tal están?" would also be correct if you're addressing more than one person.
What does tal mean? Is this phrase a kind of idiom? Formerly, I learned that "Como estas?" is "How are you?"
I answered with that and it was accepted. BTW other online applications translate this exactly this way.
Hello, how is it going should be correct, to me the estas indicates the question is asked only to one person
Not a native speaker, and this is a just an anecdote so it may be inaccurate. When i visited spain, my friend from mexico told me its a regional thing. He said that "qué tal" was the way you greeted someone there, rather than "cómo estás" because that was just the way the people talked there, the same way people in english greet people differently depending on where they're from. But obviously both are perfectly acceptable, pretty much anywhere you go.
Although if it gave you the english and you translated it "hola, cómo estás" and got marked wrong, the question is wrong lol, so just report it
The first is just a bit more casual. Some people translate it as "What's up?" or "How's it going?" If you were to say "Qué tal si vamos au ciné?", that would become "How about we go to the theater?"
Someone above said they allowed "what's up?" for the question.