List of top Signals and Systems Questions on Laplace, Fourier and z-transforms

Consider a part of an electrical network as shown below. Some node voltages, and the current flowing through the \( 3\,\Omega \) resistor are as indicated. 
The voltage (in Volts) at node \( X \) is _________. 


 

Consider a continuous-time, real-valued signal \( f(t) \) whose Fourier transform \[ F(\omega) = \int_{-\infty}^{\infty} f(t) \exp(-j \omega t) \, dt { exists.} \] Which one of the following statements is always TRUE?