Concentration  of the Ag⁺ ions in a saturated solution of  ${\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_4\text{ is }2.2\times {10}^{-4}{\mathrm{molL}}^{-1}$ Solubility product of ${\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_4 \mathrm{is}$

$$\begin{gathered} {\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_4\left(\mathrm{s}\right)\rightleftharpoons 2{\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{C}}_2{\mathrm{O}}_4^{2-}\left(\mathrm{aq}\right) \\ {\mathrm{K}}_{\mathrm{SP}}={\left[{\mathrm{Ag}}^{+}\right]}^2\left[{\mathrm{C}}_2{\mathrm{O}}_4^{2-}\right] \\ \left[{\mathrm{Ag}}^{+}\right]=2.2\times {10}^{-4}\mathrm{M} \end{gathered}$$
Given that: 
$\therefore$Concentration of ${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$ions, 
$\left[{\mathrm{C}}_2{\mathrm{O}}_4^{2-}\right]=\frac{2.2\times {10}^{-4}}{2}\mathrm{M}$

$=1.1\times {10}^{-4}\mathrm{M}$
$$\begin{gathered} \therefore {\mathrm{K}}_{\mathrm{SP}}={\left(2.2\times {10}^{-4}\right)}^2\left(1.1\times {10}^{-4}\right) \\ =5.324\times {10}^{-12} \end{gathered}$$