$\begin{array}{l}\phantom{\phantom{;}x\phantom{;}+20;}{\phantom{;}x\phantom{;}-16\phantom{;}\phantom{;}}\\\phantom{;}x\phantom{;}+20\overline{\smash{)}\phantom{;}x^{2}+4x\phantom{;}+100\phantom{;}\phantom{;}}\\\phantom{\phantom{;}x\phantom{;}+20;}\underline{-x^{2}-20x\phantom{;}\phantom{-;x^n}}\\\phantom{-x^{2}-20x\phantom{;};}-16x\phantom{;}+100\phantom{;}\phantom{;}\\\phantom{\phantom{;}x\phantom{;}+20-;x^n;}\underline{\phantom{;}16x\phantom{;}+320\phantom{;}\phantom{;}}\\\phantom{;\phantom{;}16x\phantom{;}+320\phantom{;}\phantom{;}-;x^n;}\phantom{;}420\phantom{;}\phantom{;}\\\end{array}$

$x-16+\frac{420}{x+20}$