When ${\mathrm{AgNO}}_3$ reacts with 'X' ion then initially no visible change occurs due to formation of water soluble complex. Then ion 'X' may be :

The complete reaction can be given as,

$$\begin{gathered} {\mathrm{AgNO}}_3+{\mathrm{SO}}_3^{2-}\to [\underset{ }{{\left.{\mathrm{AgSO}}_3\right]}^{-}} \\ \stackrel{{\mathrm{Ag}}_2{\mathrm{SO}}_3}{\mathrm{White}} \end{gathered}$$

Also,

$$\begin{gathered} {\left.{\mathrm{AgNO}}_3+{\mathrm{S}}_2{{\mathrm{O}}_3}^{2-}\to {\left[{\mathrm{AgCS}}_2{\mathrm{O}}_3\right)}_2\right]}^{3-} \\ \downarrow A{g}^{+} \\ \stackrel{A{g}_2{S}_2{O}_3}{white} \end{gathered}$$

Thus, the ion x may be ${{\mathrm{SO}}_3}^{2-}\text{ or }{\mathrm{S}}_2{{\mathrm{O}}_3}^{2-}$.