The total oxide ion charge in a formula unit of Mn2O3 is 6-. What is the charge on each manganese ion ?

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.

the answer is a and have a great day