How difficult is it to get a checkmate if you have a bishop an rook against a lone rook?
I think B+R vs. R is a theoretical draw.
It's a good practical chance. Even the very, very best fail in defending it sometimes. GM's lost it in times of adjourned games. So a 60-70% winning percentage is real.
I'm not sure. But in a tournament OTB, I saw someone checkmate with a rook and knight against a rook.