SOLUTION: P · (Q ∨ R), Q ⊃ S, R ⊃ T ∴ ~T ⊃ S

Question 1142561: P · (Q ∨ R), Q ⊃ S, R ⊃ T ∴ ~T ⊃ S
Answer by Edwin McCravy(20054) (Show Source): You can put this solution on YOUR website!

 1.   P · (Q ∨ R)
 2,   Q ⊃ S
 3.   R ⊃ T        ∴ ~T ⊃ S

               | 4.  ~T               Assumption for Indirect Proof
               | 5.  ~R               3,4, Modus Tollens
               | 6.  (Q ∨ R) · P      1, Commutation
               | 7.  Q ∨ R            6, Simplification
               | 8.  R ∨ Q            7, Commutation
               | 9.  Q                8,5, Disjunctive Syllogism  
               |10.  S                
11. ~T ⊃ S               lines 4-10 Indirect Proof

Edwin

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