b.
\(\dfrac{x-1}{2x-1}-1\ge0\Leftrightarrow\dfrac{-x}{2x-1}\ge0\) \(\Rightarrow0\le x< \dfrac{1}{2}\)
c.
\(\dfrac{2}{x-6}-\dfrac{1}{x-8}>0\Leftrightarrow\dfrac{2\left(x-8\right)-\left(x-6\right)}{\left(x-6\right)\left(x-8\right)}>0\)
\(\Leftrightarrow\dfrac{x-10}{\left(x-6\right)\left(x-8\right)}>0\Rightarrow\left[{}\begin{matrix}6< x< 8\\x>10\end{matrix}\right.\)