Which property is expressed by (1 + 2) + 3 = 1 + (2 + 3)?

The equation (1 + 2) + 3 = 1 + (2 + 3) illustrates the Associative Property of Addition. This property states that when adding three or more numbers, the way in which the numbers are grouped does not change the sum.

In this case, the left side of the equation groups 1 and 2 together first, then adds 3, while the right side groups 2 and 3 together first, then adds 1. Regardless of how the numbers are grouped, the resulting total will be the same. This property is specifically related to addition, distinguishing it from the other properties listed.

For instance, the Associative Multiplication Property would be relevant if the operation involved multiplication and demonstrated that (a × b) × c = a × (b × c). The Commutative Property, meanwhile, pertains to the order of numbers and states that a + b = b + a, and the Distributive Property involves distributing multiplication over addition, such as a(b + c) = ab + ac. Therefore, recognizing the correct application of the Associative Property clarifies why this equation is an example of that specific mathematical principle.