We have,
$$
\begin{aligned}
A & =\left[\begin{array}{lll}
1 & 2 & 3 \\
1 & 3 & 5 \\
2 & 1 & 6
\end{array}\right] \\
|A| & =1(18-5)-2\langle(6-10)+3(1-6) \\
& =13+8-15=6 \\
\text { Adj } A & =\left[\begin{array}{ccc}
13 & -9 & 1 \\
4 & 0 & -2 \\
-5 & 3 & 1
\end{array}\right] \\
A^{-1}=\frac{\text { Adj } A}{|A|} & =\frac{1}{6}\left[\begin{array}{ccc}
13 & -9 & 1 \\
4 & 0 & -2 \\
-5 & 3 & 1
\end{array}\right]
\end{aligned}
$$
Now, Adj $\langle$ Adj $A)=|A| A$
$\operatorname{Adj}(\operatorname{Adj} A)=6 \mathrm{~A}$
$\langle\operatorname{Adj}\langle\text { Adj } A)\rangle^{-1}=\langle 6 A)^{-1}$
$$
=\frac{1}{36}\left[\begin{array}{ccc}
13 & -9 & 1 \\
4 & 0 & -2 \\
-5 & 3 & 1
\end{array}\right]
$$
$\therefore(\operatorname{Adj}(\operatorname{Adj} A)\rangle^{-1}=\frac{1}{36}\left[\begin{array}{ccc}13 & -9 & 1 \\ 4 & 0 & -2 \\ -5 & 3 & 1\end{array}\right]$