p q ? case 1 T T F case 2 T F F case 3 F T T case 4 F F F Look for the case(s) where the unknown expression has truth value T The only case in which the unknown expression has truth value T is case 3. Case 3 is when p is false and q is true. So we ask the question: "The simultaneous truths of what expressions cause the unknown expression to be true? Answer: the simultaneous truths of ~p and q So the unknown expression is ~p /\ q. Checking with a truth table for ~p /\ q p q ~p ~p /\ q case 1 T T F F case 2 T F F F case 3 F T T T case 4 F F T F Edwin