Expert solve this find net oxidative change

Dear Student

We are given that the ion is [Fe(CN)₆]^4-. This is a complex ion in which the central metal atom is iron (Fe) and is surrounded by six CN ligands. The cyanide ion is a negatively charged ligand which has a charge of -1. The overall charge on the complex ion is -4. Let us assume that the charge on Fe is z. Therefore we have

 z + 6 (-1) = -4 

 z - 6 = -4

 Thus z = 2 
So the charge on Fe is +2. 

But In the given equation 
$$\begin{gathered} {\left[Fe(CN{)}_4\right]}^{4-} \to F{e}^{3+} + C{O_3}^{-} + N{O_3}^{-} \\ In case of reac\tan t Oxidation state of the following is provided below \\ Fe =+2 \\ C =+2 \\ N =-3 \\ In case of products oxidation state of the following is provided below \\ Fe =+3 \\ C = +3 \\ O =-1 \\ This implies that one of the redox pair is absent. Therefore we cannot \\ identify the complete oxidative change in the given equation. \end{gathered}$$

Hope this information clears your doubt.
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