1) Redox reaction: Al + 3AgNO₃ → Al(NO₃)₃ + 3Ag.
oxidation number of aluminium change from 0 to +3 (oxidation).
oxidation number of silver changes from +1 to 0 (reduction).
2) Redox reaction: Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag.
oxidation number of zinc change from 0 to +2 (oxidation).
oxidation number of silver changes from +1 to 0 (reduction).