The circuit in the figure is that of a resistor R1 in parallel with a set of resistors R2 and R3 that are in series. Across the two there is an applied voltage of 60 V.
The current `I_(R2)` and `I_(R3)` is equal as the two are is series. As the voltage drop across R2 is 30 V, the voltage drop across R3 is also 30 V. Or R2 = R3.
The equivalent resistance R is given by `(1/R) = 1/(R1) + (1/(R2+R3))`
`60/2 = 30 = R = (1/(R1) + (1/(2*R2)))^-1`
As there is only equation and two variables R1 and R2, a unique value of R2 cannot be determined.