Which property justifies that the expression $5 + (z + 2)$ is equivalent to $(5 + z) + 2$?

Commutative Property of Addition

Associative Property of Addition

Commutative Property of Multiplication

Associative Property of Multiplication

Which property is demonstrated by the statement $x \cdot 15 = 15 \cdot x$?

Associative Property of Addition

Associative Property of Multiplication

Commutative Property of Addition

Commutative Property of Multiplication