You have 2 frequencies:
fm -> the message signal frequency (in this case 200 Hz).
fs -> the sampling frequency (in this case 300 Hz).
With a 200 Hz signal, your baseband bandwidth is 200 Hz and the passband bandwidth is 400 Hz.
When you sample anything, you create sampling marks in the Spectrum. Each sampling mark is located at a harmonic of the sampling frequency (n.fs, where n is the nth harmonic).
On the positive side of spectrum, basically you gonna have the sampling marks at 0 Hz, 300 Hz, 600 Hz, 900 Hz...
The passband message signal will repeat around each of the sampling marks, so for the harmonic n:
n = 0, 0Hz:
-200Hz and +200Hz
n = 1, 300Hz:
100Hz and 500Hz
n = 2, 600Hz:
400Hz and 800Hz
n = 3, 900 Hz:
700Hz and 1100Hz
As you can see, you are having Aliasing, for example, for n = 0, your signal is from -200 Hz to 200 Hz, BUT you have the aliased 100 Hz component there, from the n=1, etc...