The number of non-empty subsets of the set $\{1, 2, 3, 4\}$ is

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 $A \not\subset B$ and $B \not\subset C,$ then $A \not\subset C$

Write the set $\{ x:x$ is a positive integer and ${x^2} < 40\} $ in the roster form.

What universal set $(s)$ would you propose for each of the following :

The set of isosceles triangles

Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?

$\{ \{ 3,4\} \}  \subset A$

Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?

$\{ 3,4\}  \in A$