The equation can be reorganized as
(C+d*X)*(A+b*X)-eye(N)=0
or
(A+b*X)*(C+d*X)-eye(N)=0
This equation will not in general have a unique solution. It can also have no solutions. When X is 1x1, for example, it reduces to a quadratic equation.
However, you can try using FSOLVE to find one of the solutions.