the Simplification of the Induction Conclusion (Step 10)

Subgoal *1/2'
(IMPLIES (AND (CONSP A)
              (EQUAL (APP (APP (CDR A) B) C)
                     (APP (CDR A) (APP B C))))
         (EQUAL (APP (APP (CDR A) B) C)
                (APP (CDR A) (APP B C)))).

Click on the link above to use the Induction Hypothesis (which is the second of the two hypotheses above and which is identical to the rewritten conclusion).