Answer
a) $ p \lor \neg q \lor \neg r$
b) $(p \lor q \lor r) \land s$
c) $ (p \land T) \lor (q \land F)$
Work Step by Step
The dual operator replaces $\lor$ by $\land $, $\land$ by $\lor$, T by F and F by T.
a) Given: $ p \land \neg q \land \neg r$
Replace $\land$ by $\lor$
$$p \lor \neg q \lor \neg r$$
b) Given : $(p \land q \land r) \lor s$
Replace $\land$ by $\lor$ and $\lor$ by $\land$
$$(p \lor q \lor r) \land s$$
c) Given: $ (p \lor F) \land (q \lor T)$
Replace $\lor$ by $\land $, $\land$ by $\lor$, T by F and F by T.
$$ (p \land T) \lor (q \land F)$$
