1. **Problem:** Write an equivalent expression using the commutative property for $y + 9$. 2. **Commutative Property:** This property states that the order of addition or multiplication does not change the result. For addition: $$a + b = b + a$$ and for multiplication: $$ab = ba$$. 3. **Apply to $y + 9$:** Using the commutative property of addition, we can write: $$y + 9 = 9 + y$$ 4. **Explanation:** We simply swapped the order of the terms without changing the value. **Final answer:** $$9 + y$$