Нужна аргументация на тему быстротечного времени, поглощающего все самое лучшее в жизни человека. Начиная от родного дома, заканчивая близкими людьми

Если из половины  некоторого натурального числа вычесть его треть, то разность будет меньше 6, а если к 2/3 этого числа прибавить 1/5 его часть, то сумма будет больше 26. Найдите натуральное число.

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In 1967 it was exactly 100 years since the birth of Marie Sklodowska-Curie, the outstanding Polish scientist whose discoveries in physics and chemistry began the era of the utilization of atomic energy…                                                            

Marie lived to see her story repeated. Her daughter  Irene grew into a woman with the same interests as her mother's and she was deeply interested in her mother’s work. From Marie she learned all about radiology and chose science for her career. At twenty-nine she married Frederic Joliot, a brilliant scientist at the  Institute of Radium, which her parents  had founded.  Joliot Frederic was born in Paris on March 1900 and first studied engineering and then chemistry. In his experiments on artificial radioactive elements, there were obtained three more radioactive elements that did not occur naturally.                                                                                                          Together the Joliot-Curies carried on the  research work that Irene's mother had begun.  In 1935 madam Curie-Joliot and her husband won the Nobel Prize for their discovery of artificial of the great work, but she died on the eve of the award. In 1946 Joliot was appointed scientific adviser to the International Atomic Energy Commission of the United Nations.                                                                                         Our respect for the two generations of the Curies is all the greater because of their moral courage. Marie and Pierre provided an example of deep dedication to science. Marie, her daughter Irene, and Irene's husband Frederic all died from radiation sickness, the result of long years of work with radioactive substances.  Finally, Frederic Joliot-Curie was not only an outstanding scientist, but also an outstanding leader of the progressive movement. There is no parallel in the records of science to the  dynasty of the Curies.

При каких значениях а имеет смлысл выражения: 

(а) [tex]\sqrt\frac{1.2a+6}{a}[/tex]

(б) [tex]\sqrt{\frac{-3-2a}{a+4}}[/tex]

разбор слова по цифрой-3

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