Here are two favorite sentences of logicians.

Afalsestatement impliesanystatement.

Atruestatement is implied byanystatement.

1. r--> (s ^ q) is true by the first saying.

2. s <---> (r-->s) is false because (r-->s) is true but we don’t know about s.

3. ~(s^r)=(~sv~r), ~r is true so (~sv~r) is true.

4. You do this one.