1. ~C (A C)
2. ~C           // ~A
3. A C    1,2 MP
line one says: if ~C is true then the consequent is true (the statement in parentheses) Since line two is an affirmation of ~C, I know I can do MP and derive the consequent.because there is no longer anything outside the parentheses they drop away.I add my justification. Click here to go on.