Удвох папках 20 зошитив . в одний на 2 зошити бильше ниж у другий.скильки зошитив у кожний папци?

Пусть в одной папке Хтетрадей. тогда в другой Х+2                         .тогдаХ+Х+2=20                                                    2Х+2=20                                                                                           2Х=18                                                                                                  Х=18:2                                                                                             Х=9                                                                                                     9+2=11                                                                                           ответ:9 и 2 тетради