Given the terse way you posted the question - and that it looks like a school/homework question, I can guess you might be short of answers. I will go as far as providing you http://www.bitmesra.ac.in/departments/laboratory/physics/03%20&%2013%20Carey%20Foster%20bridge.pdf" [Broken].
It is a PDF file which, aside from the full explanations, has a graphic of a Carey-Foster bridge laid out.
Consider carefully what it takes to make a galvanometer deflect backwards in both those places. Then think what combinations of resistances, including the wire, would make voltages appear at those places to have that effect.
If this was a homework - type question, then this was not the place to post it! If inadvertently done, then try again in the place in the forum where lots of help will be available, provided you set out fully what you have tried, and what you understand of it so far.