Platinum and gold lie at the bottom of the reactivity series. Thus it does not react with $HNO _{3}$ and $HCl$. Again, $Zn$ is more reactive than copper. Thus, copper will be displaced by $Zn$, if $ZnSO _{4}$ is placed in a copper vessel. But $Ag ^{+}$ is less reactive than copper. Thus, copper will displace silver. The corresponding reaction is:
$2 AgNO _{3}+ Cu \rightarrow Cu \left( NO _{3}\right)_{2}+2 Ag$