I got 4+, I just worked out the moles of the dichromate and then the moles of the Mn2+. So for the dichromate it was 2x10^-3 and then the Mn2+ was 6x10^-3. And in redox I know that you have to combine the two separate redox equations to make sure the electrons and everything is balanced. So if I had 3 moles of Mn2+ I know that I must have multiplied 2e- by 3 to get 6e-, and this would match the dichromate redox equation of 6e- so I can combine them. This meant that it would be Mn2+--- Mn4+ + 2e- (because I know 2 electrons must have been lost as 2x3=6). Then Mn2+x3= 3Mn2+, now you can combine them.
Idk if this makes sense???