Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$\color{blue}{2(x+y)}$
The expression "sum of two numbers" means the operation involved is addition. Thus, if we let the numbers be $x$ and $y$, then "the sum of two numbers" means $x+y$. The expression "twice" means the operation involved is multiplication, and the number to be multiplied is $2$. Therefore, "Twice the sum of two numbers" means: $\color{blue}{2(x+y)}$