1. The problem asks us to find the largest whole number that is a factor of both 156 and 168. 2. This is the Greatest Common Divisor (GCD) or Greatest Common Factor (GCF) problem. 3. To find the GCD, we can use the prime factorization method or the Euclidean algorithm. 4. Prime factorization of 156: $$156 = 2 \times 78 = 2 \times 2 \times 39 = 2^2 \times 3 \times 13$$ 5. Prime factorization of 168: $$168 = 2 \times 84 = 2 \times 2 \times 42 = 2 \times 2 \times 2 \times 21 = 2^3 \times 3 \times 7$$ 6. Identify the common prime factors with the smallest powers: - For 2: minimum power is $2^2$ - For 3: minimum power is $3^1$ - 13 and 7 are not common 7. Multiply these common factors: $$GCD = 2^2 \times 3 = 4 \times 3 = 12$$ 8. Therefore, the largest whole number that is a factor of both 156 and 168 is **12**.