Pls solve question 13.also pls give me a rough idea on how to approach such problems.Thank you.

Assume system is attached to battery of emf E  , suppose charge Q move from point A ( left end)  and Q1 and Q2  up and down and they also distribute on next branch . Direction of flow of current must be one in any of the branch  . Form equations like Q = Q1 + Q2  and other for further branches.  And apply KVL  solve u,  you will always get correct answer unless u won't make calculation mistake.