The formula of coordination complex hexaammine platinum (IV) tetrachloroplatinate (II) is

$$\begin{gathered} \left[\mathrm{Pt}{\left({\mathrm{NH}}_3\right)}_6\right]{\left[{\mathrm{PtCl}}_4\right]}_2 \\ [\mathrm{Pt}{\left({\mathrm{NH}}_3\right)}_6{]}^{4+} \\ \mathrm{x} + 6 \times 0 = 4 \\ \mathrm{x} = 4 \\ { \left({\mathrm{PtCl}}_4\right)}^{2-} \\ \mathrm{x} + 4 (-1) = -2 \\ \mathrm{x} = -2+4=2 \end{gathered}$$