Answer
$y=2$
Work Step by Step
The rate of change of $y$ with respect to $x$ is $\frac{dy}{dx}$.
Recall that the chain rule says that $\frac{d}{dx}u^n=nu^{n-1}u'$.
So the derivative of $y^5$ is as follows.
$\frac{d}{dx}y^5=5y^4\frac{dy}{dx}$
Now we set up our equation.
$5y^4\frac{dy}{dx}=80\frac{dy}{dx}$
$5y^4=80$
$y^4=16$
$y=2$
