1. (∼∼A&C) ∴ (A∨∼∼C) 2. (A&C) 1, Double negation 3. (A) 2, Simplification 4. (A∨∼∼C) 3, Addition Edwin
Give reasons for the steps, given premises 1, 2 and 3: 1. X ⊃ (Y ⊃