what is the C/D equation in dsp?
C/D is simply a "continuous-to-discrete" time conversion. In other words, sampling! :-) You can use $T$ to sample your continuous time signal $x(t)$ into a discrete time signal $x[n]$. Just replace $t=nT$ in your $x(t)$ equation, to turn it into a discrete time signal $x[n]$. D/C is the opposite operation. I think you can move on from here. Let us know if you can work it out now or if you need further help.