a,$\left\{\begin{matrix} y=-x^{3} +3x+4& & \\ x=2y^{3}-6y-2& & \end{matrix}\right.$
b,$\left\{\begin{matrix} x^{3}(2+3y) =8& & \\ x(y^{3}-2)=6 & & \end{matrix}\right.$
c,$\left\{\begin{matrix} xy-3x-2y=16 & & \\ x^{2}+y^{2}-2x-4y=33& & \end{matrix}\right.$