Question 1195751
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1. (~P v ~R) v ~S 

2.  ~P v (~R v ~S)   1, association

3.  ~P v (~S v ~R)   2, commutation 

4.   P ⊃ (~S v ~R)  3, material implication

5.   P ⊃ ~(S • R)   4, demorgan's law

Edwin</pre>