Answer
18
Work Step by Step
(a) $|A|=\begin{vmatrix}
6 & 6\\
-2 & 1
\end{vmatrix}=6(1)-6(-2)=18$
b) Using elementary row operations:
$|A|=\begin{vmatrix}
6 & 6\\
-2 & 1
\end{vmatrix}=\begin{vmatrix}
6 & 6\\
0 & 3
\end{vmatrix}=18$
c) Using the Cofactor Expansion Theorem
$|A|=A_{11}C_{11}+A_{12}C_{12}=6.1+6.2=18$
