How to find unknown parrallel Resistor

Heres my problem I am able to figure total resistance of 75ohms using R=E/I and I know how to solve for power when I have the Resistor total. But for the life of me I cant figure out how to find missing resistor without pluging random numbers in until I get one close. How do I do this?

You can calculate the voltage across R2 and use P=V²/R.

Edit, I didn't see any missing resistor.

Mike.

Hi,
The parallel combination is in series with 65E.Find Req for parallel combination.Find the I total and it is 0.6A.find the voltage drop across 65E and it is 39V.So 6V drops there in parallel combination.Since all resistance in parallel same potential will exist in R1,R2,R3.Find power for R2 by using V^2/R
V^2=36,R=21.P=36/21=1.714W

Thanks Arumugam you explained in terms I can under stand. Its finaly starting to click!

Hi,
Thanks.In future if u hav any doubt please mail me aarupk@gmail.com.