1) write balanced chemical equation.
[tex]K_{2}CO_{3}_{(aq)}+2\ HBr_{(aq)}\ ->\ 2\ KBr_{(aq)}+CO_{2}_{(g)}+H_{2}O_{(l)}[/tex]
2) separate into ions, if possible.
[tex]2\ K^{1+}_{(aq)}+CO_{3}^{2-}_{(aq)}+2\ H^{1+}_{(aq)}+2\ Br^{1-}_{(aq)}\ ->\ 2\ K^{1+}_{(aq)}+2\ Br^{1-}_{(aq)}+CO_{2}_{(g)}+H_{2}O_{(l)}[/tex]
3) remove spectator ions.
[tex]2\ H^{1+}_{(aq)}+CO_{3}^{2-}_{(aq)}\ ->\ CO_{2}_{(g)}+H_{2}O_{(l)}[/tex]
