Ans: 7
It is a case of simultaneous solubility of salts with a common ion. Here, solubility product of CuCl is much greater than that of AgCl, it can be assumed that Cl− in solution comes mainly from CuCl.
[Cl−]=√Ksp(CuCl)=10−3M
Now, for AgCl,Ksp=1.6×10−10=[Ag+][Cl−]
=[Ag+]×10−3
⇒ [Ag+]=1.6×10−7
Hence, x = 7