Answer
$({\bf i-k})\times{\bf j}={\bf i}+{\bf k}$
.
Work Step by Step
$({\bf i-k})\times{\bf j}=\left|\begin{array}{rrr}
{\bf i} & {\bf j} & {\bf k}\\
1 & 0 & -1\\
0 & 1 & 0
\end{array}\right|$
$=(0+1){\bf i}-0+(1-0){\bf k}$
$={\bf i}+{\bf k}$
