Which of the following correctly demonstrates the Associative Property of Addition? point) (x + y) + z + r = x + (y + z) + r; x(y + z) = (xy) + z; m(xy) = (mx) * y; y - (x + 1) = (y - x) + 1

The Associative Property of Addition states that the way in which numbers are grouped in addition does not change their sum. In other words, for any numbers \(a\), \(b\), and \(c\):

\[
(a + b) + c = a + (b + c)
\]

From the options provided, the expression that correctly demonstrates the Associative Property of Addition is:

\[
(x + y) + z + r = x + (y + z) + r
\]

This expression shows that regrouping the terms does not change the overall sum, which is the essence of the Associative Property of Addition.

The other options either demonstrate different properties (like multiplication or properties related to subtraction) or do not illustrate the associative nature of addition.