In a series resonant $LCR$ circuit, the voltage across $R$ is $100\ volts$ and $R = 1k\ \Omega$ with $C=2\ \mu F$. The resonant frequency is $200\ rad/s$. At resonance the voltage across $L$ is 

The resonant angular frequency , $\omega=\dfrac{1}{\sqrt{LC}}$

$L=\dfrac{1}{\omega^2 C}=\dfrac{1}{200^2 \times 2\times 10^{-6}}=12.5 H$

At resonance , impedance $Z=R$ so the current in the circuit is

$I=\dfrac{V}{Z}=\dfrac{V}{R}=\dfrac{100}{1000}=0.1 A$

Voltage across inductor, $V_L=IX_L=I\omega L=0.1\times 200\times 12.5=250 V$