Ag⁺ ions are added to the solution with
(Br^-) = (Cl^{- ​}) = (CO3^​2-) = (AsO4)^3-= 0.1 M
which compound will precipitate at the lowest [Ag⁺]?
a) AgBr [Ksp = 5 x 10 ^-13]
b) Ag₂CO₃[Ksp = 8.1 x 10 ^-12]
c) AgCl [Ksp = 1.8 x 10 ^-10]
d) Ag₃AsO₄[Ksp = 10 ^-22]
Also explain why ??

Precipitation occurs when the ionic product of the solute exceeds the solubility product, K_sp.
Ionic product is the product of the concentrations of the ions, Q_sp = [M⁺][A^-]
For ​precipitation, Q_sp > K_sp

So, the lesser the solubility product, the lesser concentration of the ions is required.
Since concentration of anion is same, concentration of Ag⁺ will be required the least in the case that has lowest solubility product, that is Ag₃AsO₄.
So the correct answer is (d).