State whether the following set is finite or infinite:
The set of numbers which are multiples of $5$.

If $X = \{a, b, c, d\}$ and $Y = \{f, b, d, g\},$ find $X - Y$.

List all the elements of the following set:
$F = \{ x : x \text{ is a consonant in the English alphabet which precedes } k \}$

In each of the following,determine whether the statement is true or false. If it is true,prove it. If it is false,give an example.
If $A \subset B$ and $B \subset C$,then $A \subset C$.

If ${N_a} = \{an : n \in N\}$,then ${N_3} \cap {N_4} = $

If $A = \{1, 2, 3, \ldots, 10\}$,then the number of non-empty subsets of $A$ containing only odd numbers is