a resistor divider question

[cagri35]

what is the R ? and how is the solving ?

 

[Diver300]

12.5 kohms

R1 has no current in it because there is no voltage across it. So it can be ignored.

The current in R2 is 0.2 mA, and all of that has to go though R, so R has to be 12.5 kohm to have 2.5 V across it and 0.2 mA through it.

 

[colin55]

I did it a different way.
Remove the -200mv
You need 12 1k resistors and one 500R to produce 200mV at the join of each resistor.
Put the 1k into circuit with -200mV on it and the join sees 0v.
This means R is 11k5.