By definition, the Greatest Common Factor (GCF) of a set of numbers, it the largest number that divides evenly the numbers in the set.
In this case, in order to find the Greatest Common Factor of 33 and 22, you can follow these steps.
Step 1. You have to descompose the numbers into their Prime factors:
[tex]\begin{gathered} 33=3\cdot11 \\ 22=2\cdot11 \end{gathered}[/tex]Step 2. Choose the common factors with the lowest exponents. In this case you just have:
[tex]11[/tex]Therefore, you can determine that the Greatest Common Factor is:
[tex]\text{GCF}=11[/tex]