20.[填空题]若}1&-3&10&5&x-1&2&-2=0，则x=____。

将行列式展开，得
$\begin{vmatrix}1 & -3 & 1 \\ 0 & 5 & x \\ -1 & 2 & -2\end{vmatrix} = 1 \cdot \begin{vmatrix}5 & x \\ 2 & -2\end{vmatrix} - (-3) \cdot \begin{vmatrix}0 & x \\ -1 & -2\end{vmatrix} + 1 \cdot \begin{vmatrix}0 & 5 \\ -1 & 2\end{vmatrix}$
计算二阶行列式：
$\begin{vmatrix}5 & x \\ 2 & -2\end{vmatrix} = 5 \times (-2) - x \times 2 = -10 - 2x$
$\begin{vmatrix}0 & x \\ -1 & -2\end{vmatrix} = 0 \times (-2) - x \times (-1) = x$
$\begin{vmatrix}0 & 5 \\ -1 & 2\end{vmatrix} = 0 \times 2 - 5 \times (-1) = 5$
代入得：
$1 \times (-10 - 2x) + 3 \times x + 1 \times 5 = -10 - 2x + 3x + 5 = x - 5$
令其等于0，解得：
$x - 5 = 0 \implies x = 5$

答案： $x = 5$