The net equations are obtained from the double displacement of the cations and anions, then balance.
NH3(aq) + HC2H3O2 (aq) = NH4+(aq) + C2H3O2-(aq)
H+(aq) + C2H3O2-(aq) + NH3(aq) -> NH4+(aq) + C2H3O2-(aq)
2NaOH(aq) + H2SO4 (aq) = Na2SO4 (s)+ 2H2O (aq)
H2S (aq) + Ba(OH)2 (aq) = BaS (s)+ 2H2O (aq)