a: \(C=\dfrac{2x+1}{x}:\dfrac{x^2-3x+4-x}{x\left(x-2\right)}\)
\(=\dfrac{2x+1}{x}\cdot\dfrac{x\left(x-2\right)}{x^2-4x+4}=\dfrac{2x+1}{x-2}\)
b: \(D=\dfrac{x+2}{x}:\dfrac{x^2-1+2x+1}{x\left(x+1\right)}\)
\(=\dfrac{x+2}{x}\cdot\dfrac{x\left(x+1\right)}{x\left(x+2\right)}=\dfrac{x+1}{x}\)