damn sounds like i got this almost completely wrong...
i had a good look at my sheet at the back
saw lead was in the middle of Fe3+ and Fe2+
this is what i did
the potential difference between Pb and Fe3+ was some answer
then because Fe2+ was on top of Pb i found the potential difference here and minused it from my first one... because it was going in the opposite direction therefore opposing.
another thing i was thinking of doing was saying the Fe3+/Pb was greater than the other so i was only gonna use that but instead decided the test was easy up till here and mabe... owell i got anode and cathode