Answer
Absolute maximum: $f(0)=5$
Absolute minimum: $f(-3) = -76$
Work Step by Step
Using closed interval method, as $f$ in continuous over the given range, let's first calculate the value of $f$ at critical numbers followed by values of $f$ at endpoints of the given range.
For critical numbers, $f'(x)=0$ or $f'(x)$ should not exist. Let's differentiate $f(x)=x^3-6x^2+5$ with respect to $x$ keeping $[-3,5]$ as interval.
$$\frac{df}{dx}=3x^2-12x$$ $\frac{df}{dx}$ exists on the given interval. Thus, $\frac{df}{dx}=0$, $$3x^2-12x=0\implies x=0, 4.$$
Thus, $f(0)=0^3-6\times 0^2+5=5$. Similarly, $f(4)=-27$. At endpoints,
$f(-3)=-76$ & $f(5)=-20$. Thus, absolute maximum $=f(0)=5$ and absolute minimum $=f(-3)=-76$.