Answer
$\{x\in \mathbb{R}\ |\ x\neq 5\}$
Work Step by Step
The domain of a rational expression is the whole set of real numbers, excluding the numbers that yield zero in the denominator.
Here, we exclude $x$ for which the denominator is equal to zero.
To find the number/s to be excluded, set the denominator equal to zero, then solve the equation:
$x-5=0$
$x=5$
Thus, $5$ has to be excluded from the domain.
Hence, the domain of the given expression is $\{x\in \mathbb{R}\ |\ x\neq 5\}$.