"Are they old?"
Translation:Ony jsou staré?
This translation could be any gender, since there is no gender information in the English sentence.
If I'm reading your screenshot correctly, it looks like you used ony in your answer, and the system (graciously) gave you a "correction" that uses staré and "passed" your answer with a typo. Why it did that, instead of rejecting your answer outright, is a mystery (at least to me).