Answer
$$\left[ \begin {array}{ccc} 1&-1\\ 2&0
\end {array} \right].$$
Work Step by Step
Let $A$ be a matrix given by
$$A =\left[ \begin {array}{ccc} 0&1\\ -2& 1
\end {array} \right].$$
Now, the cofactor matrix of $A$ can be calculated by
$$\left[ \begin {array}{ccc} 1&2\\ -1& 0
\end {array} \right]$$
hence the adjoint matrix of $A$ is given by
$$\left[ \begin {array}{ccc} 1&-1\\ 2&0
\end {array} \right].$$
