Question

Найдите значение выражения

Answer 1

$1) frac{3}{4} - frac{4}{5} = frac{15}{20} - frac{16}{20} = - frac{1}{20}$
$- frac{1}{20} times 7.8 = - frac{1}{20} times 7 frac{8}{10} = \ - frac{1}{20} times frac{78}{10} = - frac{39}{100}$
$frac{2}{3} + frac{4}{7} = frac{14}{21} + frac{12}{21} = frac{26}{21} = 1 frac{5}{21}$
$1 frac{5}{21} times ( - frac{7}{13} ) = - frac{26}{21} times frac{7}{13} = - frac{2}{3}$
$- frac{39}{100 } - ( - frac{2}{3} ) = - frac{117}{300} + frac{200}{300} = \ frac{83}{300}$
$frac{16}{21 } - frac{1}{12} = frac{64}{84} - frac{7}{84} = frac{57}{84}$

$2) frac{3}{7} - frac{16}{21} = frac{9}{21} - frac{16}{21} = - frac{7}{21} = - frac{1}{3}$
$- frac{1}{3} times ( - 2 frac{2}{7} ) = frac{1}{3} times frac{16}{7} = frac{16}{21}$
$frac{11}{15} + frac{3}{10} = frac{22}{30} + frac{9}{30} = frac{31}{30} = 1 frac{1}{30}$
$1 frac{1}{30} div ( - 12 frac{2}{5} ) = frac{31}{30} div ( - frac{62}{5} ) = \ frac{31}{30} times ( - frac{5}{62} ) = - frac{1}{12}$