решите пропорцию 2,8:у=1 3/4:5

$2.8 : y = 1 \frac{3}{4} : 5$

$2.8 * 5 = 1 \frac{3}{4} * y$

$14 = 1 \frac{3}{4} * y$

$y = 14 : 1 \frac{3}{4}$

$y = \frac{14}{1} : \frac{7}{4}$

$y = \frac{14}{1} * \frac{4}{7}$

$y = \frac{14*4}{1*7} = \frac{56}{7}$

$y = 8$

Проверка:
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$2,8 : 8 = 1 \frac{3}{4} : 5$

$2.8 : 8 = 0.35$

$1 \frac{3}{4} : 5 = \frac{7}{4} : \frac{5}{1} = \frac{7}{4} * \frac{1}{5} = \frac{7}{20} = 0.35$

0.35 = 0.35
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