Chapter 1 - Introduction to Algebraic Expressions - 1.2 The Commutative, Associative, and Distributive Laws - 1.2 Exercise Set - Page 17: 34

$4(uv)$

The associative law of multiplication states that $a\times(b\times c)=(a\times b)\times c$ (where $a$, $b$, and $c$ are real numbers). That is, changing the grouping of numbers to be multiplied does not affect the answer. Therefore, $(4u)v=(4\times u)\times v=4\times(u\times v)=4(uv)$.