Question

If n(A) = 12, n(b) = 9 and n(AuB) = 16 then find the value of n (A-B)​

Answer 1

Question has a slight error .we should find n(A
`\cap`B)

• n(A)=12
• n(B)=9.
• $n(A\cup B)=16$

`\boxed{\sf n(A\cup B)=n(A)+n(B)-n(A\cap B)}`

`\\ \rm\longmapsto n(A\cap B)=n(A)+n(B)-n(A\cup B)`

`\\ \rm\longmapsto n(A\cap B)=12+9-16`

`\\ \rm\longmapsto n(A\cap B)=5`