If A and B are finite sets such that A ⊂ B, then n(A ∪ B) = _____________
Given:
\[ A \subset B \]
This means every element of set \(A\) is already present in set \(B\). Therefore,
\[ A \cup B = B \]
Taking cardinal numbers on both sides:
\[ n(A \cup B) = n(B) \]
Answer
\[ \boxed{n(B)} \]