Answer
See the answer below.
Work Step by Step
Oxidation half-reaction (loss of electrons or increase in oxidation number) is:
$Ni(s)\rightarrow Ni^{2+}(aq)+2e^{-}$
Reduction half-reaction (gain of electrons or decrease in oxidation number) is:
$2Ag^{+}(aq)+2e^{-}\rightarrow 2Ag(s)$
