The solution is above but I am having trouble getting the so

The solution is above, but I am having trouble getting the solution, any help with work provided would be appreciated.

Solution

a)For aliasing not to occur minimum nyquist frequency=2f,where \'f \' is maximum frequency of input signal

in the problem input frequency f=200*pi/(2*pi)

f=100 hz

Fsmin=2f=200 hz

Wg=300-200=100 hz.