Question 1140109
<pre> 1. N⊃(∼R⊃C) 
 2. ∼C  
                / ∼R ⊃ ∼N     

 3. N⊃(~∼R∨C)      1, material implication
 4. N⊃(R∨C)        3, double negation
 5. ~N∨(R∨C)        4, material implication
 6. (~N∨R)∨C        5, assiation
 7. C∨(~N∨R)        6, commutation
 8. ~N∨R            7,2, disjunctive syllogism
 9. R∨~N            8, commutation
10. ~~R∨~N          9, double negation
11. ~R⊃~N          10, material implication

Edwin</PRE>