SOLUTION: Premises: 1. A ⊃ X 2. X ⊃ (B ⊃ C) Prove: (A • B) ⊃ C

1.  A —> X           Premise

2. X —> (B —> C)     Premise

3.:: A & B           Conditional Proof (CP) assumption #1

4.:: A               3, AND Elimination (AE)

5.:: X               4,1 Modus Ponens (MP)

6.:: B —> C          5,2 MP

7.:: B               3, AE

8.:: C               7,6  MP

8. (A & B) —> C      3-8, CP