Answer
a) $11$
b) $-7$
Work Step by Step
a) The determinate for a square matrix for $m$ columns anfd $n$ rows is defined as:
$det(A)= \begin{vmatrix}p&q\\r&s\end{vmatrix}=ps-rq$
a) $det(A)=\begin{vmatrix}2&1\\-3&4\end{vmatrix}=8+3=11$
b) $det(A)=\begin{vmatrix}1&0&2\\3&2&1\\0&-3&4\end{vmatrix}=(1)\begin{vmatrix}2&1\\-3&4\end{vmatrix}-0\begin{vmatrix}3&1\\0&4\end{vmatrix}+2\begin{vmatrix}3&2\\0&-3\end{vmatrix}\\=8+3-18\\-7$
