Answer
$y' = \frac{p}{q}~x^{(p/q)-1}$
Work Step by Step
$y^q = x^p$
We can find an expression for $y'$:
$qy^{q-1}~y' = px^{p-1}$
$y' = \frac{p}{q}~\frac{x^{p-1}}{y^{q-1}}$
$y' = \frac{p}{q}~\frac{x^{p-1}}{y^q/y}$
$y' = \frac{p}{q}~\frac{(x^{p-1})~(y)}{y^q}$
$y' = \frac{p}{q}~\frac{(x^{p-1})~(x^{p/q})}{x^p}$
$y' = \frac{p}{q}~(x^{-1})~(x^{p/q})$
$y' = \frac{p}{q}~x^{(p/q)-1}$