Answer
$a \times( b \times c) \ne (a \times b) \times c$
Work Step by Step
$b\times c=\begin{vmatrix} i&j&k \\ 2& 1&-1\\0&1&3\end{vmatrix}= \lt 4,-6,2 \gt$
$a \times( b \times c)=\begin{vmatrix} i&j&k \\ 1& 0&1\\4&-6&2\end{vmatrix}= \lt 6,2,-6 \gt$
$a\times b=\begin{vmatrix} i&j&k \\ 1& 0&1\\ 2& 1&-1\end{vmatrix}= \lt -1,3,1 \gt$
$(a \times b) \times c=\begin{vmatrix} i&j&k \\ -1& 3&1\\0&1&3\end{vmatrix}= \lt 8,3,-1 \gt$
Hence, $a \times( b \times c) \ne (a \times b) \times c$
