Thinking Mathematically (6th Edition)

$\left\{x| a \lt x \le b\right\}$
RECALL: The solution set $\left\{x| a \lt x \le b\right\}$ includes all real numbers $x$ that are greater than $a$ and less than or equal to $b$. Thus, the missing expression in the given statement is: $\left\{x| a \lt x \le b\right\}$