The standard reduction potentials of Zn and Ag in water at 298 K are, 
$$\begin{gathered} {\mathrm{Zn}}^{2+}+2{\mathrm{e}}^{-}\to \mathrm{Zn};{\mathrm{E}}^0=-0.76\mathrm{V} \mathrm{and} \\ {\mathrm{Ag}}^{+}+{\mathrm{e}}^{-}⟶\mathrm{Ag};{\mathrm{E}}^0=+0.80\mathrm{V} \end{gathered}$$

Which of the following reactions take place? 

The standard reduction potential ( E^o ) of silver is greater than the standard reduction potential of zinc.
Hence, Ag⁺ is stronger oxidizing agent than Zn²⁺. Hence, the reduction of Ag⁺ to Ag and the oxidation of Zn to Zn²⁺ takes place.

The reaction is ; 

$Z{n}_{\left(s\right)}+\hspace{0.17em}2A{g}_{\left(aq\right)}^{+}\to Z{n}_{\left(aq\right)}^{2+}+\hspace{0.17em}2A{g}_{\left(s\right)}$