If A, B are two sets, prove that `AuuB=(A-B)uu(B-A)uu(AnnB)`.
Hence or otherwise prove that
`n(AuuB)=n(A)+n(B)-n(AnnB)`
where, n(A) denotes the number of elements in A.

Explanation

To prove the statement \( A \cup B = (A - B) \cup (B - A) \cup (A \cap B) \), we will break it down step by step.

### Step 1: Understand the Components
- **Set A**: All elements in set A.
- **Set B**: All elements in set B.
- **Set \( A - B \)**: Elements that are in A but not in B.
- **Set \( B - A \)**: Elements that are in B but not in A.
- **Set \( A \cap B \)**: Elements that are in both A and B.
...