a, $\left\{\begin{matrix} x^{3}+x+2-\frac{4}{y}=0 & & \\ 1+y^{2}-y^{3}(4x-2)=0& & \end{matrix}\right.$
b, $\left\{\begin{matrix} 3x^{3}y^{3}=2x^{3}+y^{3} & & \\ x+y=2xy^{3}& & \end{matrix}\right.$
c, $\left\{\begin{matrix} x+y+\sqrt{x^{2}-y^{2}}=12 & & \\ y\sqrt{x^{2}-y^{2}}=12 & & \end{matrix}\right.$