1. The problem is to understand what $n(A)$ means in set theory or probability. 2. $n(A)$ represents the number of elements in the set $A$. It is called the cardinality of the set $A$. 3. To find $n(A)$, you count how many distinct elements are in the set $A$. 4. For example, if $A = \{1, 2, 3, 4\}$, then $n(A) = 4$ because there are 4 elements. 5. This concept is important because it helps quantify the size of sets and is used in probability to find the total number of outcomes. 6. If you have a specific set $A$, list its elements and count them to find $n(A)$.