#### Answer

Associative Property of Addition

#### Work Step by Step

(x+2y)+3z = x+(2y+3z)
The Associative property states that when adding (or multiplying) three numbers, it doesn't matter which two get added first. Since no minus signs are involved, we can safely assume that both sides are equal if we plugin for x, y, and z. We write the answer as The Associative Property of Addition.
(a+b)+c = a+(b+c)