If A = {4,6,9,2,7 } and B = {8,2,4,6,9} , then `A-B ` is _________.

Answer

To find \( A - B \), we need to follow these steps:

1. **Identify the sets**:
- Set \( A = \{4, 6, 9, 2, 7\} \)
- Set \( B = \{8, 2, 4, 6, 9\} \)

2. **Understand the operation \( A - B \)**:
- The operation \( A - B \) means we need to remove all elements from set \( A \) that are also present in set \( B \).

3. **List the elements of set \( A \)**:
- The elements of set \( A \) are: 4, 6, 9, 2, and 7.

4. **Check each element of \( A \) against set \( B \)**:
- **Element 4**: Present in \( B \), so remove it from \( A \).
- **Element 6**: Present in \( B \), so remove it from \( A \).
- **Element 9**: Present in \( B \), so remove it from \( A \).
- **Element 2**: Present in \( B \), so remove it from \( A \).
- **Element 7**: Not present in \( B \), so keep it in \( A \).

5. **Compile the remaining elements**:
- After removing the elements that are in \( B \), the only element left in \( A \) is 7.

6. **Write the final result**:
- Therefore, \( A - B = \{7\} \).

So, the answer is \( A - B \) is \( \{7\} \).