Examine whether the following statement is true or false:
${1, 2, 3} \subset {1, 3, 5}$

Consider the sets $\phi, A=\{1,3\}, B=\{1,5,9\}, C=\{1,3,5,7,9\}$. Insert the symbol $\subset$ or $\not\subset$ between the following pair of sets: $A \dots C$.

Which of the following sets is a subset of all other sets?

Write the following set in roster form:
$B = \{x : x \text{ is a natural number less than } 6\}$

If $A = \{ x : x \text{ is a natural number} \}$,$B = \{ x : x \text{ is an even natural number} \}$,$C = \{ x : x \text{ is an odd natural number} \}$,and $D = \{ x : x \text{ is a prime number} \}$,find $A \cap D$.

If $aN = \{ ax : x \in N \}$,then the set $3N \cap 7N$ is .....$N$.