"The hotels next to the sea are expensive."
Translation:A szállodák a tenger mellett drágák.
I've come across it in a multiple-choice exercise, in one of the wrong (distractor) options.
If it was in one of the options that are supposed to be correct, I think that is a mistake in the course - it's fine to accept more synonyms than you teach (for people who already know Hungarian and/or who are supplementing their Duolingo learning with other sources), but those words should not be required knowledge.
I would suggest reporting such things with a free-form report, though I'm not sure how much good that does.
I'm also not quite sure how multiple-choice questions are generated. I think they only come from those sentences which are marked as the best translation, in which case it may be sufficient for the course maintainers to move the sentence with hotel to non-best status for it to stop showing up.