Question

Вычислите вычислите вычислите вычислите​

Answer 1

В двойных скобках то, что делается в уме, для подробности пишу.

a)

$\frac{7}{15} - \frac{13}{15} = \frac{7 - 13}{15} = \frac{ - 6}{15} = - \frac{6}{15} = (( - \frac{6 \div 3}{15 \div 3})) = - \frac{2}{5}$

b)

$\frac{5}{7} + \frac{9}{7} = \frac{5 + 9}{7} = \frac{14}{7} = (( \frac{14 \div 7}{7 \div 7} )) = \frac{2}{1} = 2$

c)

$- \frac{1}{38} - \frac{29}{38} = (( \frac{ - 1}{38} + \frac{ - 29}{38} )) = \frac{ - 1 - 29}{38} = \frac{ - 30}{38} = - \frac{30}{38} = (( - \frac{30 \div 2}{38 \div 2} )) = - \frac{15}{19}$

d)

$\frac{13}{27} + \frac{15}{27} - \frac{7}{27} - \frac{17}{27} = (( \frac{13}{27} + \frac{15}{27} + \frac{ - 7}{27} + \frac{ - 17}{27} )) = \frac{13 + 15 - 7 - 17}{27} = \frac{4}{27}$

e)

$\frac{3}{13} + \frac{57}{26} \times \frac{4}{19} = \frac{3}{13} + \frac{57 \times 4}{26 \times 19} = (( \frac{3}{13} + \frac{57 \div 19 \times 4 \div 2}{26 \div 2 \times 19 \div 19} )) = \frac{3}{13} + \frac{3 \times 2}{13 \times 1} = \frac{3}{13} + \frac{6}{13} = \frac{3 + 6}{13} = \frac{9}{13}$

f)

$\frac{7}{19} \times 5 - \frac{4}{5} \div \frac{76}{85} = \frac{7 \times 5}{19} - \frac{4}{5} \times \frac{85}{76} = \frac{ 35}{19} - \frac{4 \times 85}{5 \times 76} = (( \frac{35}{19} - \frac{4 \div 4 \times 85 \div 5}{5 \div 5 \times 76 \div 4} )) = \frac{35}{19} - \frac{1 \times 17}{1 \times 19} = \frac{35}{19} - \frac{17}{19} = \frac{35 - 17}{19} = \frac{18}{19}$