\(\dfrac{7}{x}+\dfrac{3}{x-3}-\dfrac{4x-3}{x^2-3x}\)
\(=\dfrac{7\left(x-3\right)}{x\left(x-3\right)}+\dfrac{3x}{x\left(x-3\right)}-\dfrac{4x-3}{x\left(x-3\right)}\)
\(=\dfrac{7x-21+3x-4x+3}{x\left(x-3\right)}\)
\(=\dfrac{6x-18}{x\left(x-3\right)}\)
\(=\dfrac{6\left(x-3\right)}{x\left(x-3\right)}\)
\(=\dfrac{6}{x}\)