Three resistors are connected as shown in the diagram. If the current from the power supply is 250 mA and the current through R3 is 54 mA, what is the resistance of R3?
1/Req= 1/R1 + 1/R2 +1/R3
The Attempt at a Solution
First I used the parallel circuit formula of 1/Req= 1/R1+ 1/R2 + 1/R3
but there are two variables (Req and R3) so I'm not sure how to use that. Also, there's no voltage provided so I'm a bit confused as how to go from here. Any help would be appreciated :)