Answer
$(d-3)(d-9)$
Work Step by Step
Using the factoring of trinomials in the form $x^2+bx+c,$ the $\text{
expression
}$
\begin{align*}
d^2-12d+27
\end{align*} has $c=
27
$ and $b=
-12
.$
The two numbers with a product of $c$ and a sum of $b$ are $\left\{
-3,-9
\right\}.$ Using these two numbers, the factored form of the $\text{
expression
}$ above is
\begin{align*}
&
(d-3)(d-9)
\end{align*}