Answer
$(j-k ) \times (k-i)=i+j+k$
Work Step by Step
Cross product of a vector with itself is zero.
We are given $(j-k ) \times (k-i)$
$(j-k ) \times (k-i)=j \times (k-i)-k \times (k-i)$
$=j \times k-j \times i-k\times k+k \times i$
$=i-(-k)-0+j$
$=i+j+k$
Hence,$(j-k ) \times (k-i)=i+j+k$