Answer
See answer below.
Work Step by Step
This problem requires observation of the stoichiometric ratio between ions and the solute.
a) $0.50\ M NH_4^+, 0.25\ M\ SO_4^{2-}$
b) $0.246\ M\ Na^+, 0.123\ M\ CO_3^{2-}$
c) $0.056\ M\ H_3O^+, 0.056\ M\ NO_3^-$