Question

выполните действия: (7/8-13/20)+9/10, (7/18-1/12)+5/6, (3/4-8/15)+17/20

так делать
(7/15-1/6)+2/5=(7•2-1•5)
15•2 6•5​

Answer 1

Пошаговое объяснение:

1)

$( \frac{3}{4} - \frac{8}{15} ) + \frac{7}{20} = \frac{3}{4} - \frac{8}{15} + \frac{7}{20} = \frac{3 \times 15 - 8 \times 4 + 7 \times 3}{60} = \frac{45 - 32 + 21}{60} = \frac{34}{60} = \frac{34 \div 2}{60 \div 2} = \frac{17}{30}$

2)

$( \frac{7}{8} - \frac{13}{20}) + \frac{9}{10} = \frac{7}{8 } - \frac{13}{20} + \frac{9}{10} = \frac{7 \times 5 - 13 \times 2 + 9 \times 4}{40} = \frac{35 - 26 + 36 }{40} = \frac{45}{40} = \frac{45 \div 5}{40 \div 5} = \frac{9}{8} = 1 \frac{1}{8}$

3)

$( \frac{3}{4} - \frac{8}{15} ) + \frac{7}{20} = \frac{3}{4} - \frac{8}{15} + \frac{7}{20} = \frac{3 \times 15 - 8 \times 4 + 7 \times 3}{60} = \frac{45 - 32 + 21}{60} = \frac{34}{60} = \frac{34 \div 2}{60 \div 2} = \frac{17}{30}$