Question 1029581
1. A ⊃ U   ------------------Hypothesis
2. ~A v U -------------------Material implication 
3. (~A v U) v (~K) ----------Disjunctive amplification
4.  ~A v (U v ~K)-------------Associativity
5.  ~A v (~KvU) --------------Commutativity
6.  A ⊃ (K ⊃ U)  ------------Material implication (twice)