You mix together the following three solutions (the order of mixing doesn't matter):
100.0 mL 0.100 M Na2SO4, 50.0 mL 0.300 M ZnCl2, 100.0 mL 0.200 M Ba(CN)2
Of all the possible salts that can form from these cations and anions, only two are insoluble: zinc cyanide and barium sulfate. Thus, both of those salts will precipitate out of solution. Calculate the molarity of each ion remaining in the solution following complete precipitation of these two insoluble compounds. Note: Some of the ions will have been completely consumed by the precipitation reactions; thus their concentrations will be effectively zero.