You need to check the operation of the Random module with this code, and it does not start, Python shouts that the problem is in the 14 line, but that I do not understand
I work in 3.5.2.3.
The code itself is below

import random
Import Matplotlib.pyPlot AS PLT
Low = 12; HIGH = 68;
Fig = Plt.gcf ()
Fig.set_size_inches (14,5)
For k in Range (3,6):
PLT.SUBPLOT (1, 3, K - 2)
N = 10 ** k
N = RANGE (N)
RND = [RANDOM.UNIFORM (LOW, HIGH) FOR I IN N]
Plt.plot (N, RND, 'B.' ')
Plt.axis ([0, N, 10, 70])
Plt.xlabel ('$ n $'),
PLT.YLabel ('$ RND $')

Answer 1, Authority 100%

This error says that you have problems with retreats . In Python, cycles (and not only) are separated by indentation. For example, the body for you need to separate 4 spaces (ideally). I do not know how and cho there you have, but I think it will be correct (at least a mistake will eliminate)

import random
Import Matplotlib.pyPlot AS PLT
Low = 12.
High = 68.
Fig = Plt.gcf ()
Fig.set_size_inches (14,5)
For k in Range (3,6):
  PLT.SUBPLOT (1, 3, K - 2)
  N = 10 ** k
  N = RANGE (N)
  RND = [RANDOM.UNIFORM (LOW, HIGH) FOR I IN N]
  Plt.plot (N, RND, 'B.' ')
  Plt.axis ([0, N, 10, 70])
  Plt.xlabel ('$ n $'),
  Plt.ylabel ('$ RND $')

Also, points with commas are not needed absolutely, they worsen the readability of the code. I advise you to read PEP8