Well, think of 24 as the denominator of the fraction, so James sleeps 8 hours of the whole 24 making it 8/24(a) which can be simplified by finding a common factor between the two numbers: 8
making the fraction now 1/3 so James sleeps 1/3 of the day(b). Thinking about it this way, the only option for the fraction that he doesn't sleep is the other 2/3 of the day(c).