"Potete lasciare i piatti qui."
Translation:You can leave the plates here.
I wonder the same thing. I believe this is just a case of DuoLingo not getting it right. English doesn't differentiate between singular and collective "you" -- prompting most of us to say "you all" when we are translating the collective you.
Duolingo got it right: I think the "You all" is not American English but Southern American English
When there's a form of potere, is there never a di/a etc... before the infinitive?