$\left\{\begin{matrix}b=\frac{7x}{12b_{1}}\text{, }&b_{1}\neq 0\\b\in \mathrm{C}\text{, }&x=0\text{ and }b_{1}=0\end{matrix}\right.$

$\left\{\begin{matrix}b_{1}=\frac{7x}{12b}\text{, }&b\neq 0\\b_{1}\in \mathrm{C}\text{, }&x=0\text{ and }b=0\end{matrix}\right.$

$\left\{\begin{matrix}b=\frac{7x}{12b_{1}}\text{, }&b_{1}\neq 0\\b\in \mathrm{R}\text{, }&x=0\text{ and }b_{1}=0\end{matrix}\right.$

$\left\{\begin{matrix}b_{1}=\frac{7x}{12b}\text{, }&b\neq 0\\b_{1}\in \mathrm{R}\text{, }&x=0\text{ and }b=0\end{matrix}\right.$