As you know, the equiv wt is the amount to react completely with one equiv of something else. But first, you have to determine what that something is.
With coordination compounds, its assumed that we're talking about the capacity for ligand transfer. (Coord compounds can also do electron transfer in which case the equiv wt would be different).
for K4Fe[CN]6 , there are six cordination sites for the six ligands (CN).
So eq wt = MW/6 . That's the amount to react completely with one equiv of a donor.
NH]4PbCl6 is again 6 sites. MW/6
Mo4O3(C2O4)212H2O
This one is tricky. C2O4 is a bidentate ligand. 2 of them makes a total of four sites. But is O cosidered a ligand or a fixed oxide? I'm not 100% sure but I don't think it is a coordination ligand. Is H2O (12 of them) a ligand? I think its water of crystallization by the way it's written, not ligand.
So, eq wt = MW/4