Question 668746
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1.   ~~G
2.   (P * Y) v (X -> ~W)
3.   (P * Y) -> ~G
4.   ~W -> ~G                  /~X
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5.   ~~W                      4,1     Modus Tollens
6.   ~(P * Y)                 2,1     Modus Tollens
7.   X -> ~W                  2,6     Disjunctive Syllogism
8.   ~X                       7,5     Modus Tollens
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