"This person is old."
Translation:यह आदमी बूढ़ा है।
If Duolingo expected "यह आदमी बूढ़ा है।", the English sentence should have been "This man is old". Otherwise, the correct answer should be "यह बूढ़ा है।".
Person could also be व्यक्ति I believe (though perhaps that's more 'individual').
However, यह व्यक्ति बूढ़ी है। was not accepted. Isn't व्यक्ति a feminine noun? Or is there a mistake in some other detail? Thx