Question 199524
Note: * means "and"


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1.   C -> A 
2.   B -> C    :. (C v B) -> A
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3.   B -> A                        2,1     Hypothetical Syllogism 
4.   ~B v A                          3     Material Implication
5.   A v ~B                          4     Commutation
6.   ~C v A                          1     Material Implication
7.   A v ~C                          6     Commutation
8.   (A v ~C) * (A v ~B)           7,5     Conjunction
9.   A v (~C * ~B)                   8     Distribution
10.  (~C * ~B) v A                   9     Commutation  
11.  ~(C v B) v A                   10     De Morgan's Theorem 
12.  (C v B) -> A                   11     Material Implication
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