1. **Problem:** Find the intersection of sets $A$ and $B$ where $A = \{1, 2, 3, 4, 5\}$ and $B = \{1, 3, 5, 7, 9\}$. 2. **Formula:** The intersection of two sets $A$ and $B$, denoted $A \cap B$, is the set of elements that are in both $A$ and $B$. 3. **Step:** Identify common elements in both sets. 4. **Work:** $A \cap B = \{x : x \in A \text{ and } x \in B\} = \{1, 3, 5\}$ 5. **Answer:** The intersection $A \cap B = \{1, 3, 5\}$.