Answer:
31 as it has only 2 factors which is 1 and 31
Without the discount each book is 16.25 with the discount theyre 15 each
the memory is the independent, because that can vary at will, so it's independently varying at will, whilst the amount of songs are limited to how much memory there's in the CD, so the songs are dependent on the memory availability.
The decimal conversion to 8 39/40 is 8.975 and the decimal terminates.
3/4 I believe since 6 1/4- 51/2 is 3/4