How many elements does $P(A)$ have,if $A = \varnothing$?

The dual of $(x+y) \cdot (x^{\prime} \cdot 1)$ is:

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 pair of sets: $A, \ldots B$.

Write the set $\{ \frac{1}{2}, \frac{2}{3}, \frac{3}{4}, \frac{4}{5}, \frac{5}{6}, \frac{6}{7} \}$ in the set-builder form.

Let $A = \{1, 2, 3, 4, 5, 6\}$. Insert the appropriate symbol $\in$ or $\notin$ in the blank space:
$5 \dots A$

Make correct statements by filling in the symbols $\subset$ or $\not\subset$ in the blank spaces:
$\{a, b, c\} \dots \{b, c, d\}$