{3}__A

Answer

To solve the problem, we need to determine the relationship between the number 3 and the set A, which is defined as A = {1, 3, 5, 7, 9}.

### Step-by-Step Solution:

1. **Identify the Set A**:
The set A is given as A = {1, 3, 5, 7, 9}. This means that the elements of the set A are 1, 3, 5, 7, and 9.

2. **Identify the Element to Compare**:
We need to compare the number 3 with the elements of set A.

3. **Check if 3 is an Element of A**:
We look at the elements of set A:
- The elements are 1, 3, 5, 7, and 9.
- We can see that 3 is indeed one of the elements in set A.

4. **Determine the Appropriate Symbol**:
Since 3 is an element of set A, we use the symbol "∈" (which means "belongs to") to indicate that 3 is a member of the set A.

5. **Final Answer**:
Therefore, we can fill in the blank with the symbol "∈". The complete expression will be: {3} ∈ A.

### Summary:
The correct symbol to insert in the blank is "∈", indicating that 3 belongs to the set A.

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