2. Originally Posted by m777
$B\times C=\{(a,m),(a,n),(b,m),(b,n)\}$
$A\times (B\times C)=\{ (1,(a,m)),(1,(a,n)),(1,(b,m)),(1,(b,n))$ $(2,(a,m)),(2,(a,n)),(2,(b,m)),(2,(b,n))$ $(3,(a,m)),(3,(a,n)),(3,(b,m)),(2,(b,n))\}$