For the redox reaction
$MnO_4^-+C_2O_4^{2-}+H^+\rightarrow Mn^{2+} +CO_2 + H_2O$
The correct coefficients of the reactants for the balanced equation are
$MnO_4^-$ $C_2O_4^{2-}$ $H^+$
n-factor of $MnO_4^-\Rightarrow 5$
n-factor of $C_2O_4^{2-}\Rightarrow 2$
Ratio of n-factors of $4MnO_4^-$ and $C_2O_4^{2-}$ is 5 : 2. So, molar ratio in balanced reaction is 2 : 5.
∴ The balanced equation is
$2MnO_4^-+5C_2O_4^{2-}+16H^+\rightarrow 2Mn^{2+}+ 10 CO_2 +8 H_2O$