Some terminology and conventions:
- q ? p is called the converse of p ? q
- ?q ? ?p is called the contrapositive of p ? q
What is p ? q ? r , the disjunction of p and q ?r, or the
conjunction of p ?q and r?
The former should be expressed as p ? (q ? r), and the
The operator ? is applied before all the other operators,
so that, e.g., ?q ? r means (?q) ? r rather than ?(q ? r)