Answer:
Mn= +3 charge
Explanation:
if you take what we know, and that would be the charge of oxygen, we know that oxygen has a 2- charge and there are 3 sets of O^2- so multiply the number of oxygen times the charge and you get 6-.
Next set up an equation as listed in the picture which will be 2(x)=6
and that is the charge of the Mn ion.