Which property states that changing the grouping of numbers does not change the value of the expression?

The Associative Property states that when performing addition or multiplication, the way in which the numbers are grouped does not affect the outcome of the operation. For example, in addition, (a + b) + c is the same as a + (b + c). This property allows you to rearrange the grouping of numbers without changing the final result, demonstrating how expressions can be evaluated in different ways while maintaining their equivalence.

In contrast, other properties like the Commutative Property pertain to the order of the numbers, while the Distributive Property involves multiplying a single term by a sum or difference, and the Identity Property focuses on maintaining the original value of a number when adding zero or multiplying by one. Thus, the Associative Property is specifically about grouping, making it the correct choice for this question.