Translation:I want to cancel my room booking.
I think "I want to cancel my room reservation" or "I need to cancel my room reservation" should be accepted too
And might even be more idiomatic than the given translation e.g. in American English.
If I were already talking to the staff of a hotel, or anyone who already knows I have a reservation, I would most likely just say, "I want to cancel my room."
"I need to unbook a room.", "I want to cancel a reservation.", "I want to cancel a room booking." are the most direct ways to say this. I reported all three.
For the second and third sentences, Duolingo wants me to use "my" instead of "a" even though we have no idea whose reservation is being canceled.
I don't think "unbook" is proper English, the other two should be accepted.
It should be I want to cancel my reservation. At least in American English. "I want to cancel my room booking" is horribly awkward.
"I want to cancel a room booking" should be accepted. Who says it's my own?
"I want to cancel booking my room" I think is reasonable too. Would more often mean cancelling while in the process of booking, but is slightly less clunky than the given wording (for me, in the US, and using just the provided word blocks).