For series resistors, the equivalent resistance is the summation of the resistances. Therefore:
For parallel resistors, the equivalent resistance is 1 over the sumation of 1 over the resistances:
We know that the voltage across R6 is V4. Therefore, according to Ohm's Law:
`I_T = V_4/R_6`
`(R_4(R_2+R_3))/(R_2+R_3+R_4) = V_4/I_T`
Now, substitute what we know:
We don't have enough information to solve any further than that; therefore, `R_2 ` and `R_4` are any such values that satisfy the above equation.
R2 AND R4 CAN HAVE A SET OF ANY VALUES
eg:- R2 =40 ohm, R4=20 ohm or other values satisfying relationship:-
------------- = 15
hope this helps.