"Where is the fire?"
Translation:Càit a bheil an teine?
It’s just an older spelling of the same words. You can use either càit a bheil (newer spelling) or càite a bheil (older one). Both are used in the course as at the start it used the older càite a bheil but then moved to changing it to càit a bheil, so you’ll see both in the course, and in each place both should be accepted.
It is explained in the tips and notes for the Home skill:
Càite a bheil?
The Gaelic Orthographic Conventions document (not a page turner) recommends this now be written as Càit a bheil. This is pronounced the same and both spellings are frequently seen, although the one we have used is more retro. We will probably update this in the next iteration of the course.
You can access the tips and notes in the web browser version of Duolingo (sadly not in the mobile app currently), or on the duome website.