The ending of rook and knight's pawn against rook, with the defending king in front of the pawn, is normally drawn - so long as the defender plays his rook correctly.
A second (or even, as here) a third pawn on the same file will in most cases make no difference, though there are exceptions.
In this classic endgame Blackburne taught his long-time rival Bird a lesson about such endings, and the seven-man tablebase even reveals one variation in which the third pawn could come in handy,
(1) Bird,Henry Edward - Blackburne,Joseph Henry [C31]
Generated with ChessBase 10
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