Answer
a. 2$\times$3
b.
$a_{32}$ does not exist,
$a_{23}$= $\displaystyle \frac{1}{2}$
Work Step by Step
A matrix of order $m\times n$ has $m$ rows and $n$ columns.
$a_{ij}$ is the element of the matrix in row i, column j.
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a.
the matrix has m = 2 rows and n = 3 columns, so
its order is 2$\times$3
b.
$a_{32}$= the element in row 3 (does not exist), column 2,
does not exist,
$a_{23}$= the element in row 2, column 3 = $\displaystyle \frac{1}{2}$