I also get 3/4 R.
If the circuit is not balanced, I can't see much use for it! Usually, these "bridge" type circuits are only useful when balanced. [eg Wheatstone bridge]
To attempt to answer the question, though, one possibility would be to set up a system of Kirchhoff's Law equations for the various closed loops (where ΣIR = 0) as well as the main circuit supplying the pd that provides the main current.
You would get 6 equations with 6 unknowns and a relationship between the main current and the applied pd. This would give the equivalent R.