Assuming N is the domain of Natural numbers 0,1,...
Assuming Z is the domain of Integers ...2,1,0,1,2,...
a) 8/x is a natural number when x is positive and x=1,2,4,8. So the required range set is {8,4,2,1}.
b) 8 ≤ p^{3} ≤ 125 when p is positive and 2 ≤ p ≤ 5. The cube of a number is the same sign as the number.
So if p is an integer the required set of values p can have is {2,3,4,5}, and the range is: {8,27,64,125). If p can be any real number, then the domain is the subset of [2,5] where the cube of the number is an integer, and the range is p^{3} can be any integer in the range [8,125];
1/20/2014

Kenneth G.