4 HBrIIIO2-II 2 Br20 + 3 O20 + 2 H2O-II

This is an oxidation-reduction (redox) reaction:

4 BrIII + 12 e- 4 Br0 (reduction)

6 O-II - 12 e- 6 O0 (oxidation)

Change the oxidation states