Oxidation : 
${\mathrm{CH}}_3{\mathrm{COO}}^{-}+3\overline{\mathrm{O}}\mathrm{H}\to {\mathrm{CH}}_3{\mathrm{COO}}^{-}+2{\mathrm{e}}^{-}+2{\mathrm{H}}_2\mathrm{O}$

Reduction : $\left.{\left[\mathrm{Ag}{\left({\mathrm{NH}}_3\right)}_2\right]}^{+}+{\mathrm{e}}^{-}⟶\mathrm{Ag}+{\mathrm{NH}}_3\right]\times 2$

${\mathrm{CH}}_3\mathrm{CHO}+2{\left[\mathrm{Ag}{\left({\mathrm{NH}}_3\right)}_2\right]}^{+}+3\overline{\mathrm{O}}\mathrm{H}⟶{\mathrm{CH}}_3\mathrm{O}\overline{\mathrm{O}}+2{\mathrm{H}}_2\mathrm{O}$

Molecular mass $\left(\mathrm{M}\right)$ of ${\mathrm{CH}}_3\mathrm{CHO}=44 \mathrm{g} {\mathrm{mol}}^{-1}$

Equivalent weight $\left(\mathrm{E\omega }\right)=\frac{\mathrm{M}}{\mathrm{n}-\mathrm{factor}}=\frac{44}{2}=22 \mathrm{g} {\mathrm{mol}}^{-1}$

Since aldehyde is getting oxidised therefore, it is acting as reducing agent and not oxidising agent.