Let, in sample mols of FeSO4 and FeC2O4 be x and y respectively.
FeSO4nf=1+FeC2O4nf=3+KMnO4⟶Fe+3++4CO2+Mn+2
So, (no. of eqv. of FeSO4 + no. of eqv. of FeC2O4) = no. of eqv. of KMnO4
x×1+y×3=83 .....(1)
x+y=53 .....(2)
Using (1) an (2), we get x=7/6; y=1/2