$$\left. \begin{array} { l } { 3 y = y + \frac { 1 } { q + \frac { 1 } { x } } } \end{array} \right.$$
$x=\frac{2y}{1-2qy}$
$y\neq 0\text{ and }\left(q=0\text{ or }y\neq \frac{1}{2q}\right)$
