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Please show me how to borrow a book.
Literal
Book [attributive-の] borrowing-way [object-を] teach-[please-てください].
借り方 = 借り (stem of 借りる, 'borrow') + 方 ('way, method'). The pattern [verb masu-stem]+方 is a productive way to form 'the way of doing X / how to X.' 教えてください is the polite 'please teach/tell me.' A standard library or instructional query.