I do not understand set-builder notation.....

Question

Using correct mathematical notation and symbols, express the following in set-builder notation: Z = {16, 17, 18, 19, 20}

Answer 1

Instead of enumerating the members, the set-builder notation defines the members of a set using mathematical conditions.
The set of all odd integers would be:
A={x∈ℤ : mod(x,2)≡1}
or the integers between 40 and 45:
B={x∈ℤ : 40≤x≤45}

For more examples, see:
http://en.wikipedia.org/wiki/Set-builder_notation

Answer 2

x¡Êℤ : 9<x¡Ü20