with this material odds, you can learn: how strong the Rook and the Bishop are, piece coordination, and basic checkmating ideas.
First, let’s see how it goes with automatic moves.
1.K6b 2.R2b+ 3.K7c 4.B5e 5.K7d
As you can see, you can check whenever you want, but the white king runs away easily.
6.+R7b 7.K6e 8.B3c+ 9.K5f
It’s getting hard to checkmate the white king. generally, check in a row doesn’t work. You need to trap the king.
Let’s get back to the position after 1.K6b
let’s think for a moment. Where the white king goes on the next move? The white king wants to go to the C-rank. so? The question becomes how to prevent it.
2.R2c+
this move is important to remember. Now the promoted Rook dominates the white King’s escape routes.
3.K7b 4.B5e 5.K6b 6.B7c+
all white can do is to just wait. 4.B2b+ instead of 4.B5e is fully playable but not 4.B3c+ because Black wants to keep the promoted Rook’s control on C- rank.
if white plays 4.B3c+, Black can run away.
7.K5b 8.+B6c 9.K4b 10.+B5c 11.K5a 12.+R2a
There are many winning moves for Black. This text continuation is instructive. White puts the promoted Bishop where it can’t be taken because of the promoted Rook. That is basic piece coordination. And attacking from both sides is the key point to checkmate the king.