a) $P(x)=(6x^{5}-\frac{1}{2}x^{4}+\frac{1}{3}x^{3})/(2x^{3})=3x^{2}-\frac{1}{4}x+\frac{1}{6}$
$P(-2)=3\times (-2)^{2}-\frac{1}{4}\times (-2)+\frac{1}{6}=\frac{38}{3}$
b) $Q(x) =3(\frac{2x}{3}-1)+(15x^{2}-10x)/(-5x)-(3x-1)=2x-3-3x+2-3x+1=-4x$
$Q(\frac{1}{3})=-4\times \frac{1}{3}=-\frac{4}{3}$