Answer
a)$MnO_{4}^{-}(aq)+3e^{-} \rightarrow MnO_{2}(s)$ , $IO_{3}^{-}(aq) \rightarrow IO_{4}^{-}(aq)+2e^-$
b)$NO_{3}^{-}(aq)+e^- \rightarrow NO_{2}(g)$ , $SO_{2}(aq) \rightarrow SO_{4}^{-}(aq)+3e^-$
Work Step by Step
a)$Mn$ is reduced from 7+ to 4+ and $I$ is oxidized from 5+ to 7+
b)$N$ is reduced from 5+ to 4+ and $S$ is oxidized from 4+ to 7+
