MnIVO2 + 2 KBr-I + 2 H2SO4 MnIISO4 + Br20 + K2SO4 + 2 H2O

This is an oxidation-reduction (redox) reaction:

2 Br-I - 2 e- 2 Br0 (oxidation)

MnIV + 2 e- MnII (reduction)

Change the oxidation states