#### Answer

$(-\infty, 12]$

#### Work Step by Step

The radicand (expression inside a radical sign) of a square root cannot be negative as its root is an imaginary number.
This means that the radicand, which is $24-2x$, must be greater than or equal to 0.
Thus,
$24-2x\ge 0
\\-2x \ge 0-24
\\-2x \ge -24$
Divide both sides by $-2$. Note that since a negative number is being divided on both sides of an inequality, the inequality sign flips to the opposite direction.
$\dfrac{-2x}{-2} \le \dfrac{-24}{-2}
\\x \le 12$
Therefore, the domain of the given function is $(-\infty, 12]$.