1. The problem statement, all variables and given/known data Determine whether the following is valid: [tex] p \rightarrow \neg q , r \rightarrow q , r, \vdash \neg p [/tex] 2. Relevant equations Modus Ponens, disjunctive syllogism, double negation. 3. The attempt at a solution I've boiled it down to [tex] p \rightarrow \neg q , q, \vdash \neg p [/tex] However I do not understand how the book says to use disjunctive syllogism and double negation here. I've expanded the implication into its fundamental forum but I still cant see it.