**Method 1:**

List the factors of each number.

Factors of 28: 2, 4, 7, 14, 28

Factors of 42: 2, 3, 6, 7, 14, 21, 42

Identify the greatest common factor.

The greatest common factor of 28 and 42 is 14.

**Method 2:**

Write the prime factorization of each number.

28 = 2 × 2 × 7.

42 = 2 × 3 × 7.

The GCF is the product of the common prime factors in each number.

GCF = 2 × 7 = 14.

The greatest common factor of 28 and 42 is 14.

The greatest common factor of 28 and 42 is 14.

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