Write two examples to show that:
whole numbers are closed under addition.

Answer

To show that whole numbers are closed under addition, we need to demonstrate that when we add two whole numbers, the result is always a whole number. Here are two examples:

### Example 1:
1. Take the first whole number: **9**.
2. Take the second whole number: **6**.
3. Add the two whole numbers:
\[ 9 + 6 = 15 \]
4. Check the result: **15** is also a whole number.

### Example 2:
1. Take the first whole number: **12**.
2. Take the second whole number: **13**.
3. Add the two whole numbers:
\[ 12 + 13 = 25 \]
4. Check the result: **25** is also a whole number.

### Conclusion:
In both examples, we started with whole numbers and ended up with whole numbers after addition. This shows that whole numbers are closed under addition.

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