Problems on sets: counting elements and comparing sets. Specifically, find n(N) for N = 11, 12, 13, 14, n(S) for S = 1, 4, 9, ..., 49, and determine if A = e, f, g, h equals B = g, f, h, e, and if X =

$N = \{11, 12, 13, 14\}$

There are 4 elements in set $N$.

b)

The set $S = \{1, 4, 9, \dots, 49\}$ consists of perfect squares.
The elements are $1^2=1$, $2^2=4$, $3^2=9$, $4^2=16$, $5^2=25$, $6^2=36$, $7^2=49$.
So, $S = \{1, 4, 9, 16, 25, 36, 49\}$.

There are 7 elements in set $S$.

3. Let's say and write whether the following sets are equal or not.

a)

Both sets contain exactly the same elements: $e, f, g, h$. The order of elements does not matter in a set.

Since all elements are identical, sets A and B are equal.
A and B are $\boxed{\text{equal}}$

b)

Set X contains elements $3, 6, 9, 12$. Set Y contains elements $1, 3, 5, 7$.

The sets do not contain exactly the same elements (e.g., 6, 9, 12 are in X but not Y; 1, 5, 7 are in Y but not X).
X and Y are $\boxed{\text{not equal}}$

4. Let's say and write whether the following sets are overlapping or disjoint.

a)

There are no elements that are present in both set P and set Q.

Since they have no common elements, P and Q are disjoint.
P and Q are $\boxed{\text{disjoint}}$

b)

The element 20 is present in both set A and set B.

Since they have at least one common element (20), A and B are overlapping.
A and B are $\boxed{\text{overlapping}}$