#### Answer

$\left\{x| a \lt x \le b\right\}$

#### Work Step by Step

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:
$\left\{x| a \lt x \le b\right\}$