1: assumption 2: 3: assumption assumption assumption 4: 5: 6: 7: 8: 9: 10: 11: 12: ((((A-B) -A) -A)-B)-B intro 1-11 Select one or more: line 6 and line 10 contains the same propositional formula The box-proof contains 4 boxes. line 5 and line 11 contains the same propositional formula line8 is justified by an application of the elim rule The box proof contains 5 boxes and one of the hidden annotations is an assumption line 6: ((A + B) A) - A line 8 is justified by an application of the intro rule line 4: (A + B) A The following box-proof uses only the implication rules (e.g. no classical contradiction). 1: 2: assumption assumption assumption assumption 3: 4: 5: 6: 7: 8: 9: 10: 11: 12: ((((A-B)--A)-A)-B)-B intro 1-11 Select one or more: line 6 and line 10 contains the same propositional formula O The box-proof contains 4 boxes. line 5 and line 11 contains the same propositional formula O line 8 is justified by an application of the >-elim rule The box proof contains 5 boxes and one on the hidden annotations is an assumption. line 6: ((A + B) A) - A line 8 is justified by an application of the -intro rule line 4: (A + B) A