I don't understand why take with this rook is better.

lichess.org/training/61676
It's a tactical problem. At the last move, I don't understand why take with the f rook is better.

The b rook sorry.

Taking with the b rook is better because it allows Rb8+ Kh7 Rxf7

Aaah ! :O I understand, thanks cheddarman :)