Question

Show that if A BELONGS TO B Then C-B BELONGS TO C-A

Answer 1

Let x BELONGS TO C-B
xBELONGS TO C , x doesntBELONG TO B
also if A BELONGS TO B
means -B BELONGS TO -A
so xBELONGS TO C , x BELONGS TO -B
xBELONGS TO C , x BELONGS TO -A
x BELONGS TO C-A.