is the value of   R = 45Ω 

   There is no effect of 30V battery.Because 50V battery convert it into charging battery.

because there is zero current through the 30V battery, there will be zero current through the 10 ohm resistor in the left loop

therefore from Kirchhoff's voltage rule voltage drop across R= 30V, therefore R(50/(20+R))=30, solving this elementary equation, we get R= 30ohm

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