The meter reads 7.84 mA when the switch is in position A. What is the resistance of R4?

Question

R1=220 Ω
R2=470 Ω
R3=510 Ω
VS =12 V

I honestly have no clue how to solve this. Please help.

Answer 1

I honestly have no clue what your circuit looks like.

Answer 2

My fault. It's figure 73 (one on left).

photobucket.com/gallery/user/choicedelight/media/cGF0aDovU2VyaWVzIENpcmN1aXQucG5n/?ref=

Answer 3

Rt = Vs/I = 12/7.84ma = 1.53k Ohms = 1530 Ohms = Total resistance.
R4 = Rt-(R1 + R2 + R3) = 1530 - 1200 = 330 Ohms.