For an integer $n$ let $S_n=\{n+1, n+2, \ldots \ldots, n+18\}$. Which of the following is true for all $n \geq 10$ ?
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 $x \in A$ and $A \not\subset B$, then $x \in B$
Write the following intervals in set-builder form :
$\left( {6,12} \right]$
List all the elements of the following sers :
$B = \{ x:x$ is an integer $; - \frac{1}{2} < n < \frac{9}{2}\} $
How many elements has $P(A),$ if $A=\varnothing ?$