$$\left. \begin{array} { l } { x } \\ { \frac { x } { 1 + i } + \frac { y } { 1 - 2 i } = 1 } \end{array} \right.$$
$x=z$
$y=\left(\frac{1}{2}+\frac{3}{2}i\right)z+\left(1-2i\right)$
$z\in \mathrm{C}$
