By definition we have:
In mathematics, the commutative property or commutativity is a fundamental property that has some operations according to which the result of operating two elements does not depend on the order in which they are taken.
This is fulfilled in ordinary addition and multiplication: the order of the addends does not alter the sum, or the order of the factors does not alter the product.
We have then that the commutative property for this case is:
9 + 8 = 8 + 9 = 17
Answer:
A number sentence that shows the commutative property of addition is:
9 + 8 = 8 + 9 = 17