So if I change 합시다 to 합니다 does that mean the room is clean?
What's the difference between 청소하다 and 깨끗하다?
I think you can use 청소하십시오 as well as 청소합시다
하십시오 is imperative tense.
Now we are learning propositive. And yes duolingo didn't tell us what is the lesson about beforehand.
-하십시오 is a polite version of -하세요 (command), so it's not the same.
What's the difference between saying 방이 and 방을?