Chapter 1 - Introduction to Algebraic Expressions - 1.2 The Commutative, Associative, and Distributive Laws - 1.2 Exercise Set - Page 17: 69

$2a+2b$

The distributive law states that $a(b+c)=ab+ac$ (for real numbers $a$, $b$, and $c$). That is, the product of a number and a sum can be written as two products. Therefore, $(a+b)2=a(2)+b(2)=a\times2+b\times2=2a+2b$.