Answer
$\displaystyle \frac{1}{4},\qquad x\neq 4$
Work Step by Step
Complex rational expressions have rational expressions in the numerator or/and in the denominator.
Here, the numerator contains $\displaystyle \frac{x}{4}$. Multiplying with 4 would get rid of it. We also multiply the denominator with 4.
$\displaystyle \frac{4}{4}\times\frac{\frac{x}{4}-1}{x-4}=\frac{x-4}{4(x-4)}$
The expression has a common factor. Reduce.
$=\displaystyle \frac{1}{4},\qquad x\neq 4$
($4$ is excluded as $(x-4)$; it was a part of the expression before reducing.)
