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The correct format of divisor is to divide or multiply the numerator and denominator by a non-zero number until both numerator and denominator are prime numbers.

Reduction means to change a fraction into a fraction equal to it, but with smaller numerator and denominator, which is called reduction. Method of reduction: (1) Gradually reduce. Divide by the common factor of the numerator and denominator (except 1) until the numerator and denominator only have the common factor 1. (2) One-time reduction method. Directly divide by the greatest common divisor of numerator and denominator (except 1).