Answer
$$ v\times w=
- 2j.
$$
Work Step by Step
$$ v\times w=
\left|\begin{array}{rrr}{i} & {j} & {k} \\ {2} & {0} & {0} \\ {-1} & {0} & {1}\end{array}\right|=i \left|\begin{array}{rrr} {0} & {0} \\ {0} & {1}\end{array}\right|-j\left|\begin{array}{rrr} {2} & {0} \\ {-1} & {1}\end{array}\right|+k\left|\begin{array}{rrr}{2} & {0} \\ {-1} & {0} \end{array}\right|\\
=i(0)-j(2-0)+k(0)\\
=- 2j.
$$
