In an LCR series a.c. circuit, the voltage across each of the components, $L,C$ and $R$ is $50\text{V}$. The voltage across the $LC$ combination will be:

In a series LCR circuit, the voltages across the inductor ($V_L$) and the capacitor ($V_C$) are $180^{\circ }$ out of phase.The net voltage across the LC combination is:
$$V_{LC}=|V_L-V_C|$$
Given $V_L=50\text{V}$ and $V_C=50\text{V}$:
$$V_{LC}=|50-50|=0\text{V}$$