Answer
If $p$, then $q$.
Not $q$.
Therefore, not $p$.
If all prime numbers are odd, then 2 is odd.
2 is not odd.
Therefore, it is not the case that all prime numbers are odd.
Work Step by Step
Replace each complete idea (i.e., an idea that can be expressed as a complete, independent sentence) as a single letter (here, $p$ or $q$). Fill in the blanks in the example argument based on where you put the letters $p$ and $q$ by examining the first argument.