Question

Show that if 

      A ⊂ B, then C – B ⊂ C – A.

Answer 1

Let A ⊂ B  

To show:

 C – B ⊂ C – A

 Let 

x ∈ C – B

 ⇒ x ∈ C and x ∉ B 

⇒ x ∈ C and x ∉ A [A ⊂ B] 

⇒ x ∈ C – A ∴ C – B ⊂ C – A