In the series LCR circuit (figure), the voltmeter and ammeter readings are:

Here$V_L=V_C$ They are in opposite phase. Hence, they will cancel each other. Now the resultant potential difference is equal to the applied potential difference = 100 V

Z = R               $(\therefore X_L=X_C)$

$\therefore I_{rms}=\frac{V_{rms}}{Z}=\frac{V_{rms}}{R}=\frac{100}{50}=2A$