If `A={b,c,y,a,q,r}` and `B = {a,x,p}`, then n (A-B) =_______

Answer

To solve the problem, we need to find the number of elements in the set difference \( A - B \).

### Step-by-Step Solution:

1. **Identify the Sets**:
- Set \( A = \{ b, c, y, a, q, r \} \)
- Set \( B = \{ a, x, p \} \)

2. **Understand Set Difference**:
- The set difference \( A - B \) consists of elements that are in set \( A \) but not in set \( B \).

3. **List the Elements of Set A**:
- The elements in set \( A \) are: \( b, c, y, a, q, r \).

4. **Remove Elements of Set B from Set A**:
- We need to remove the elements of set \( B \) from set \( A \).
- The elements in set \( B \) are: \( a, x, p \).
- From set \( A \), we remove the element \( a \) (since \( x \) and \( p \) are not in \( A \)).
- After removing \( a \), the remaining elements in set \( A \) are: \( b, c, y, q, r \).

5. **Form the Set \( A - B \)**:
- Thus, \( A - B = \{ b, c, y, q, r \} \).

6. **Count the Elements in \( A - B \)**:
- Now, we count the number of elements in \( A - B \).
- The elements are \( b, c, y, q, r \), which gives us a total of 5 elements.

### Final Answer:
The number of elements in \( A - B \) is \( n(A - B) = 5 \).

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