To find the greatest common factor (GCF) of three numbers, you can use the prime factorization method:
1. Find the prime factorization of each number:
- 152 = 2^3 * 19
- 171 = 3 * 3 * 19
- 57 = 3 * 19
2. Identify the common prime factors: 19 is the only common prime factor.
3. Multiply the common prime factors together: 19.
Therefore, the greatest common factor of 152, 171 and 57 is 19.