(3) Given: d→ed∨fh→∼ehProve: f
7.f (5, 6, Disjunctive Syllogism)
Step 1 :1.h→∼e (Given)
Step 2 :2.h (Given)
Step 3 :3.∼e (1, 2, Modus Ponens)
Step 4 :4.d→e (Given)
Step 5 :5.∼d (3, 4, Modus Tollens)
Step 6 :6.d∨f (Given)
Step 7 :7.f (5, 6, Disjunctive Syllogism)