$\begin{array}{l}\phantom{\phantom{;}3x\phantom{;}+5;}{\phantom{;}3x\phantom{;}-7\phantom{;}\phantom{;}}\\\phantom{;}3x\phantom{;}+5\overline{\smash{)}\phantom{;}9x^{2}-6x\phantom{;}-40\phantom{;}\phantom{;}}\\\phantom{\phantom{;}3x\phantom{;}+5;}\underline{-9x^{2}-15x\phantom{;}\phantom{-;x^n}}\\\phantom{-9x^{2}-15x\phantom{;};}-21x\phantom{;}-40\phantom{;}\phantom{;}\\\phantom{\phantom{;}3x\phantom{;}+5-;x^n;}\underline{\phantom{;}21x\phantom{;}+35\phantom{;}\phantom{;}}\\\phantom{;\phantom{;}21x\phantom{;}+35\phantom{;}\phantom{;}-;x^n;}-5\phantom{;}\phantom{;}\\\end{array}$

$3x-7+\frac{-5}{3x+5}$