$\left\{\begin{matrix}p=\frac{xy}{z\left(x+y\right)}\text{, }&x\neq -y\text{ and }z\neq 0\\p\in \mathrm{R}\text{, }&\left(z=0\text{ or }y=0\right)\text{ and }\left(z=0\text{ or }x=0\right)\text{ and }\left(y=0\text{ or }x=0\right)\end{matrix}\right.$

$\left\{\begin{matrix}x=-\frac{pyz}{pz-y}\text{, }&y\neq pz\\x\in \mathrm{R}\text{, }&\left(z=0\text{ or }p=0\right)\text{ and }y=0\end{matrix}\right.$