The coordination numbers of Co and Al in [Co(Cl)(en)2]Cl and K3[Al(C2O4)3], respectively, are: (en = ethane-1,2-diamine)

en and C2O42- are bidentate ligands and Cl- is monodentate. So, the coordination number of [Co(Cl)(en)2]Cl is (2 × 2 + 1 = ) 5 and K3[Al(C2O4)3] is (2 × 3 = ) 6.