1. ( A v B ) ? ~ ( C ? D ) 2. ( C -> D) 3. ~ ( A v B ) -> E / ? E This class is for critical reasoning. By proving valid I mean in this format:

a. Premises: p ? (q ?r ), s ? r , r ? p. Prove: s ? q.

1. p ? (q ?r ) Premise

2. s ? r Premise

3. r ? p Premise

4. s Assumption

5. r Modus Ponens, 2,4

6. p Modus Ponens, 3,5

7. (q ?r ) Modus Ponens, 1,6

8. q Conjunction elimination, 7

9. s ? q Implication introduction, 4-8

That is just a sample problem but that's how I need it answered.