"An important professor."
Translation:Un profesor importante.
The way Duolingo works in that if your typo is a true typo you do not get dinged for it. But if your typo happens to make another dictionary word, then the Duolingo computer sees what you typed as being a wrong word and you get dinged for typing a wrong word.
bit harsh to count me wrong for adding an extra "s" to "profesor". Usually you get dinged for a typo!
then i make another mistake for dropping the "t" from "importante" and get dinged for a typo. Go figure!