1.

This statement is true, because the number 7 is one of the elements of set B.

2. N(A) = a

This is false. N(A) ("the cardinality of A") denotes the number of elements in set A. A correct statement would be

N(A) = 6.

3.

This is true, because every element of set B is also an element of set N ("B is a subset of N").

4.

This is false, because it is an incorrect use of the notation.

In order for the subset symbol to be used correctly, the expressions on each side of the symbol must be sets. In the given statement, the expression on the left is an element. not a set.

The following statements would be correct:

5.

This is similar to example 4. The statement is false because it is an incorrect use of the notation. In order to correctly use the element symbol, the expression on the left must be an element (not a subset) of the expression on the right.

The following statements would be correct:

6.

This is correct, because every element of {6, 8, 10} is also an element of E ("{6, 8, 10} is a subset of E").

7.

This is correct, because every element of {6, 8, 10} is also an element of {6, 8, 10} ("{6, 8, 10 is a subset of {6, 8, 10}").