a: \(\dfrac{x}{0.9}=\dfrac{5}{6}\)

\(\Leftrightarrow x=\dfrac{3}{4}\)

b: \(\dfrac{-6}{x}=\dfrac{9}{-15}\)

\(\Leftrightarrow x=10\)

c: \(\dfrac{\dfrac{14}{15}}{\dfrac{9}{10}}=\dfrac{x}{\dfrac{3}{7}}\)

\(\Leftrightarrow x=\dfrac{3}{7}\cdot\dfrac{14}{15}:\dfrac{9}{10}=\dfrac{2}{5}\cdot\dfrac{10}{9}=\dfrac{20}{45}=\dfrac{4}{9}\)

a)\(\frac{7}{3}.\left( { - 2,5} \right).\frac{6}{7} = \frac{7}{3}.\frac{6}{7}.\left( { - 2,5} \right) = 2.\left( { - 2,5} \right) =  - 5\)

b)

\(\begin{array}{l}0,8.\frac{{ - 2}}{9} - \frac{4}{5}.\frac{7}{9} - 0,2\\ = \frac{4}{5}.\frac{{ - 2}}{9} - \frac{4}{5}.\frac{7}{9}-\frac{2}{10}\\ = \frac{4}{5}.\left( {\frac{{ - 2}}{9} - \frac{7}{9}} \right) -\frac{1}{5}\\ = \frac{4}{5}.\left( { - 1} \right)-\frac{1}{5} \\= \frac{{ - 4}}{5}-\frac{1}{5}\\=\frac{-5}{5}\\=-1.\end{array}\)

a) \(\text{​​}/3x-5/-\frac{1}{7}=\frac{1}{3}\)                           b)\(\left(\frac{3}{5}x-\frac{2}{3}x-x\right).\frac{1}{7}=\frac{-5}{21}\)

  \(/3x-5/=\frac{10}{21}\)                                           \([x.\left(\frac{3}{5}-\frac{2}{3}-1\right)]=\frac{-5}{21}.7\)

 \(\Rightarrow3x-5=\frac{10}{21}hay3x-5=\frac{-10}{21}\)         \(\left[x.\frac{-16}{15}\right]=\frac{-5}{3}\)

\(3x=\frac{115}{21}\)                \(3x=\frac{95}{21}\)                         \(x=\frac{25}{16}\)

\(x=\frac{115}{63}\)                  \(x=\frac{95}{63}\)                             Vậy x = \(\frac{25}{16}\)

                      Vậy x \(\in\left\{\frac{115}{63};\frac{95}{63}\right\}\)

16384/25 =655.36

a)\(\frac{7}{12}.\frac{6}{11}+\frac{7}{12}.\frac{5}{11}-2\frac{7}{12}\)

\(=\frac{7}{12}.\left(\frac{6}{11}+\frac{5}{11}\right)-\frac{31}{12}\)

\(=\frac{7}{12}-\frac{31}{12}\)

\(=-2\)

b)\(\frac{-5}{9}.\frac{-6}{13}+\frac{5}{-9}.\frac{-5}{13}-\frac{5}{9}\)

\(=\frac{5}{9}.\left(\frac{6}{13}+\frac{5}{13}-1\right)\)

\(=\frac{5}{9}.\left(\frac{11}{13}-\frac{13}{13}\right)\)

\(=\frac{5}{9}.\frac{-2}{13}\)

\(=-\frac{10}{117}\)

c)\(0,8.\frac{-15}{14}-\frac{4}{5}.\frac{13}{14}-1\frac{2}{5}\)

\(=\frac{4}{5}.\frac{-15}{14}-\frac{4}{5}.\frac{13}{14}-\frac{7}{5}\)

\(=\frac{4}{5}.\left(-\frac{15}{14}-\frac{13}{14}\right)-\frac{7}{5}\)

\(=\frac{4}{5}.\left(-2\right)-\frac{7}{5}\)

\(=\frac{-8}{5}-\frac{7}{5}\)

\(=-3\)

d)\(-75\%.\frac{6}{7}+5\%.\frac{6}{7}+\frac{7}{10}.1\frac{1}{7}\)

\(=\frac{-15}{20}.\frac{6}{7}+\frac{1}{20}.\frac{6}{7}+\frac{7}{10}.\frac{8}{7}\)

\(=\frac{6}{7}.\left(\frac{-15}{20}+\frac{1}{20}\right)+\frac{4}{5}\)

\(=\frac{6}{7}.\frac{-7}{10}+\frac{4}{5}\)

\(=-\frac{3}{5}+\frac{4}{5}\)

\(=\frac{1}{5}\)

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