The stoichiometric numbers appearing from left to right in the reaction 

${\mathrm{MnO}}_4^{2-}+{\mathrm{H}}^{+}\to {\mathrm{MnO}}_4^{-}+{\mathrm{MnO}}_2+{\mathrm{H}}_2\mathrm{O}$  are

The balanced equation is $3{\mathrm{MnO}}_4^{2-}+4{\mathrm{H}}^{+}\to 2Mn{O}_4^{-}+{\mathrm{MnO}}_2+2{\mathrm{H}}_2\mathrm{O}$ 

A chemical reaction's equation is said to be balanced if both the reactants and the products have the same total charge and atom count for each component. In other words, the mass and charge of the reaction are identical on both sides.