I don't think you use a fraction. You multiply .6666 by 72 which equals 47.9952 or rounded 48. :)
Entirely impossible to know, there are an infinite number of sequences which have the terms 8, 15, and 22 for n=1,2,3 -you could say that if you wanted to give a "smart" answer and it would be true
otherwise 43 pages on 6th day I think