This provides you right guidence, try it once
For illustration, the set of numbers 0, 1, 2, 3, 4, 5, 6 and 7 can be represented given as:
P = {0, 1, 2, 3, 4, 5, 6, 7} , enumerative method
P = {X/x = 0, 1, 2...7} descriptive method
Or
P = {x/0 ≤ x ≤7} where x is an integer.