Chapter 1 - Introduction to Algebraic Expressions - Review Exercises: Chapter 1 - Page 76: 20

The answer is $\color{red} {2x + (y + z)}$.

The Associative Law of Addition states that changing groupings of a sum does not affect the answer. In this item, we can switch the groupings of the terms: \begin{align} (2x + y) + z &= \color{red} {2x + (y + z)} \end{align}