Need to find a proof for the sequent p→(q ∨ r), ((¬p)∨(¬q)) ⊢ ¬r I started a book on logic in computer science I went over the rules of propositional logic but I can't seem to be able to prove this sequent. Can anyone help me or give me some starting points? (no truth tables please)

The sequent is false. If you take $p$ False and $r$ True then both antecedents are true but the succedent is False.