1. (P ∨ Q) ⊃ R 2. S ⊃ ~R 3. S ∨ P / Q ⊃ P | 4. Q Assumption for Conditional Proof | 5. Q ∨ P 4, Addition | 6. P ∨ Q 5, Commutation | 7. R 6,1 Modus ponens | 8. ~~R ⊃ ~S 2, Transposition | 9. R ⊃ ~S 8, Double negation |10. ~S 9,7 Modus ponens |11. P 3,10 Disjunctive syllogism 12. Q ⊃ P lines 4-11 Conditional proof Edwin