"I am sorry, but you are not old enough for this."
Translation:סליחה, אבל אתם לא מבוגרים מספיק בשביל זה.
Yoav, the first sentence that you say was not accepted is identical to Duo's official "correct" one, so I'm puzzled by your comment. But I agree with RegiCorvus, מספיק מבוגר(ים) sounds OK to me and in fact that was what I entered, but was slapped down as wrong. Any native speakers out there care to comment please: does מספיק have to come after the adjective, or can it precede it?
Thanks Mr Sadun for that quick reply. Appreciate it . However i notice that in DL mitstyr was never offered as an option. I did try Reverso, a dictionary that i often use, where מצטער and סליחה were offered as correct solutions.
(ליחה דוקטור, אני מניח שקצת נסחפתיבo)
DL differs ! Is it region specific as in the case of Brit English and American English ?