MnO4^- + SO3^2- -> Mn^2+ + SO4^2-

(7+).........(4+)...........(2+)........(6+)(ignore the periods they are there for spaces that wouldnt show up??)

They tell me to write the oxidation numbers and determine which ones change. I have seen whut the numbers are They are written below the equation. I write how much each element increases or decreases by Mn decreases by 5 and S increases by 2. It says find the lowest common multiple of the decrease and increases os the oxidation numbers. which is 10. NEXT IS WHERE IM CONFUSED!

im supposed to determine the net charge for the left and right side it says the left side is 12- and the right side is 6-??? I cant even think of how to determine the net charge, and i need to know how to do this for the questions i do have to answer its probably simple but can someone please help??