This puzzle is a review of a basic chess endgame principle. If you recognize it, you can draw as White.
It's all about recognizing that king and bishop and h-pawn(s) can only draw against the lone king if the queening square is the opposite color of the bishop. 1.Rd8+ Rc8 2.Rxc8+ Kxc8 3.Ba6 Kb8 4.Bxb7 Kxb7 It doesn’t matter how many pawns are on the h-file. The king won’t be budged from a1.