Question 237510
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1.   (O . P) -> Q
2.   R -> (Q -> S)
3.   O . R               / P -> S
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4.   O                          3     Simplification
5.   R . O                      3     Commutation
6.   R                          5     Simplification
7.   O -> (P -> Q)              1     Exportation
8.   P -> Q                     7,4   Modus Ponens
9.   Q -> S                     2,6   Modus Ponens
10.  P -> S                     8,9   Hypothetical Syllogism
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