"How old are you?"
Agreed. For those of us trying to type the answers (not using the Word Bank, in order to better learn spelling), these off-topic questions are especially frustrating. You are already struggling with typing out 한글, you spend time typing out the long honorific form, and then are told it is wrong because the question was very unclear. Poor pedagogy!
I believe this is due to technical reasons: every sentence can only have one default answer. Given "How old are you" turns up earlier without the honorifics, that's why it's throwing it up again instead of the one you've given (which should be the correct answer for this course).
I think because this is supposed to be a more casual way of asking people similar in age to you how old they are. It was probably included in "honorific" because they wanted to teach both ways, which is why I'm surprised a mod hasn't addressed this in the comments, or information page.