The problem asks about the property used to rewrite the expression $(6+9) + 5$ as $6 + (9+5)$.

Step 1: Recognize the Property

In the expressions:

• Line 1: $(6+9) + 5$
• Line 2: $6 + (9+5)$

The grouping of numbers (parentheses) changes from $(6+9) + 5$ in Line 1 to $6 + (9+5)$ in Line 2. Since only the grouping of numbers has changed without altering the order of numbers themselves, the Associative Property of Addition is being applied.

Step 2: Explanation

The Associative Property of Addition states that changing the grouping of the numbers being added does not change their sum. In symbols, it is expressed as: $(a + b) + c = a + (b + c)$ Here:

• $(6+9) + 5$ was rewritten as $6 + (9+5)$, so we are applying this property.

Final Answer:

The expression was rewritten using the Associative Property of Addition.

---

Would you like further clarification or details on this explanation?

Here are 5 related questions to expand your understanding:

1. How does the Associative Property differ from the Commutative Property?
2. Can the Associative Property be used with subtraction or only addition?
3. What is the result of calculating both expressions: $(6+9) + 5$ and $6 + (9+5)$?
4. How does the Associative Property apply to multiplication?
5. Can the Distributive Property change the order of addition like the Associative Property?

Tip: When dealing with parentheses in addition, always check whether changing their grouping affects the result—it often leads to using the Associative Property!