Question

find the greatest common factor of 30 and 39.

Explanation:

Step1: List factors of 30

Factors of 30: $1, 2, 3, 5, 6, 10, 15, 30$

Step2: List factors of 39

Factors of 39: $1, 3, 13, 39$

Step3: Identify common factors

Common factors: $1, 3$

Step4: Select the largest common factor

The greatest value in $\{1, 3\}$ is $3$.

Answer:

3