设剩下的练习本是打x折出售的，可得：
0.25×1200×40%×80%+[0.25×（1+40%）×x-0.25]×1200×（1-80%）=0.25×40%×1200×86%
                                  96+（0.35x-0.25）×1200×20%=103.2
                                        96+（0.35x-0.25）×240=103.2
                                                   96+84x-60=103.2
                                                         84x=67.2
                                                           x=80%．
答：剩下的练习本是打8折出售的．