$\begin{array}{l}\phantom{\phantom{;}3x^{2}-2x\phantom{;}-12;}{\phantom{;}4x\phantom{;}+\frac{7}{3}\phantom{;}\phantom{;}}\\\phantom{;}3x^{2}-2x\phantom{;}-12\overline{\smash{)}\phantom{;}12x^{3}-x^{2}-12x\phantom{;}+17\phantom{;}\phantom{;}}\\\phantom{\phantom{;}3x^{2}-2x\phantom{;}-12;}\underline{-12x^{3}+8x^{2}+48x\phantom{;}\phantom{-;x^n}}\\\phantom{-12x^{3}+8x^{2}+48x\phantom{;};}\phantom{;}7x^{2}+36x\phantom{;}+17\phantom{;}\phantom{;}\\\phantom{\phantom{;}3x^{2}-2x\phantom{;}-12-;x^n;}\underline{-7x^{2}+\frac{14}{3}x\phantom{;}+28\phantom{;}\phantom{;}}\\\phantom{;-7x^{2}+\frac{14}{3}x\phantom{;}+28\phantom{;}\phantom{;}-;x^n;}\frac{122}{3}x\phantom{;}+45\phantom{;}\phantom{;}\\\end{array}$

$4x+\frac{7}{3}+\frac{\frac{122}{3}x+45}{3x^2-2x-12}$