$\begin{array}{l}\phantom{\phantom{;}x\phantom{;}+3;}{\phantom{;}x^{2}-6x\phantom{;}+18\phantom{;}\phantom{;}}\\\phantom{;}x\phantom{;}+3\overline{\smash{)}\phantom{;}x^{3}-3x^{2}\phantom{-;x^n}-6\phantom{;}\phantom{;}}\\\phantom{\phantom{;}x\phantom{;}+3;}\underline{-x^{3}-3x^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-x^{3}-3x^{2};}-6x^{2}\phantom{-;x^n}-6\phantom{;}\phantom{;}\\\phantom{\phantom{;}x\phantom{;}+3-;x^n;}\underline{\phantom{;}6x^{2}+18x\phantom{;}\phantom{-;x^n}}\\\phantom{;\phantom{;}6x^{2}+18x\phantom{;}-;x^n;}\phantom{;}18x\phantom{;}-6\phantom{;}\phantom{;}\\\phantom{\phantom{;}x\phantom{;}+3-;x^n-;x^n;}\underline{-18x\phantom{;}-54\phantom{;}\phantom{;}}\\\phantom{;;-18x\phantom{;}-54\phantom{;}\phantom{;}-;x^n-;x^n;}-60\phantom{;}\phantom{;}\\\end{array}$

$x^{2}-6x+18+\frac{-60}{x+3}$