Question

Номер 513 все четыре даю 10 баллов

Answer 1

Пошаговое объяснение:

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Answer 2

$\left(\dfrac{5}{21} + \dfrac{2}{15}\right) + \dfrac{2}{21} = \left(\dfrac{5}{21} + \dfrac{2}{21}\right) + \dfrac{2}{15} = \dfrac{7}{21} + \dfrac{2}{15} = \dfrac{1}{3} + \dfrac{2}{15} = \dfrac{5}{15} + \dfrac{2}{15} = \dfrac{7}{15}$

$\left(\dfrac{2}{35} + \dfrac{3}{28}\right) + \dfrac{1}{28} = \left(\dfrac{3}{28} + \dfrac{1}{28}\right) + \dfrac{2}{35} = \dfrac{4}{28}\right + \dfrac{2}{35} = \dfrac{1}{7}\right + \dfrac{2}{35} = \dfrac{5}{35}\right + \dfrac{2}{35} = \dfrac{7}{35} = \dfrac{1}{5}$

$\left(\dfrac{7}{30} + \dfrac{8}{45}\right) + \left(\dfrac{2}{45} + \dfrac{1}{30}\right) = \left(\dfrac{7}{30} + \dfrac{1}{30}\right) + \left(\dfrac{2}{45} + \dfrac{8}{45}\right) = \dfrac{8}{30} + \dfrac{10}{45} = \dfrac{4}{15} + \dfrac{10}{45} = \dfrac{12}{45} + \dfrac{10}{45} = \dfrac{22}{45}$

$\left(\dfrac{5}{24} + \dfrac{11}{60}\right) + \left(\dfrac{13}{60} + \dfrac{1}{24}\right) = \left(\dfrac{5}{24} + \dfrac{1}{24}\right) + \left(\dfrac{13}{60} + \dfrac{11}{60}\right) = \dfrac{6}{24} + \dfrac{24}{60} = \dfrac{1}{4} + \dfrac{2}{5} = \dfrac{5}{20} + \dfrac{8}{20} = \dfrac{13}{20}$