Answer:
never
Step-by-step explanation:
The expression: ~q means "not q"
If ~q is false, then q is true
The expression:
If p is true and ~q is false
is equivalent to:
If p is true and q is true
then:
If p is true and q is true, then p -> q is never false (or is always true, see table attached). Or:
If p is true and ~q is false, then p -> ~q is never false.
