Chapter 1 - Introduction to Algebraic Expressions - 1.2 The Commutative, Associative, and Distributive Laws - 1.2 Exercise Set - Page 17: 37

$2[3(a+b)]$

$3[2(a+b)]=2[3(a+b)]$ There are three factors in this multiplication problem. They are 3, 2 and (a+b). The associative property says the factors can be regrouped without impacting the result. In the original expression 2 is grouped with (a+b). In the rewritten expression 3 is grouped with (a+b).