$Ca_3(PO_4)_2\rightleftharpoons 3Ca^{2+} + 2PO_4^{3-}$      $k_{sp}=(3S)^3\times  (2S)^2=108s^5$    $\therefore \,\,s\, = \,\,{\left( {\frac{{{K_{sp}}}}{{108}}} \right)^{1/5}}$

$Hg_2Cl_2\rightleftharpoons Hg_2^{2+}+2Cl^-$     $k_{sp} =  S \times (2s)^2 = 4s^3$  $\therefore \,\,\,s\,\, = \,\,{\left( {\frac{{{K_{sp}}}}{4}} \right)^{1/3}}$

$Ag_3PO_4  \rightleftharpoons   3Ag^++PO_4^{3-}$     $k_{sp} = (3s)^3 \times s = 27s^4$ $\therefore \,\,s\,\, = \,\,{\left( {\frac{{{K_{sp}}}}{{27}}} \right)^{1/4}}$

$Cus \rightleftharpoons  Cu^{2+}+s^{2-} \,\,,k_{sp}=s^2$ $\therefore \,\,s\,\, = \,\,\sqrt {ksp} $