Question

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Answer 1

1: \(x+\dfrac{1}{12}=-\dfrac{3}{8}\)

=>\(x=-\dfrac{3}{8}-\dfrac{1}{12}=-\dfrac{9}{24}-\dfrac{2}{24}=-\dfrac{11}{24}\)

2: \(x-2=-\dfrac{5}{9}\)

=>\(x=-\dfrac{5}{9}+2=-\dfrac{5}{9}+\dfrac{18}{9}=\dfrac{13}{9}\)

3: \(\dfrac{2}{15}-x=-\dfrac{3}{10}\)

=>\(x=\dfrac{2}{15}+\dfrac{3}{10}=\dfrac{4}{30}+\dfrac{9}{30}=\dfrac{13}{30}\)

4: \(-x+\dfrac{4}{5}=\dfrac{1}{2}\)

=>\(-x=\dfrac{1}{2}-\dfrac{4}{5}\)

=>\(x=\dfrac{4}{5}-\dfrac{1}{2}=\dfrac{8}{10}-\dfrac{5}{10}=\dfrac{3}{10}\)

5: \(x+\dfrac{1}{3}=\dfrac{2}{5}-\left(-\dfrac{1}{3}\right)\)

=>\(x+\dfrac{1}{3}=\dfrac{2}{5}+\dfrac{1}{3}\)

=>\(x=\dfrac{2}{5}\)

6: \(\dfrac{3}{7}-x=\dfrac{1}{4}-\left(-\dfrac{3}{5}\right)\)

=>\(\dfrac{3}{7}-x=\dfrac{1}{4}+\dfrac{3}{5}=\dfrac{5}{20}+\dfrac{12}{20}=\dfrac{17}{20}\)

=>\(x=\dfrac{3}{7}-\dfrac{17}{20}=\dfrac{60}{140}-\dfrac{119}{140}=\dfrac{-59}{140}\)

7: \(x\cdot\dfrac{-3}{7}=\dfrac{5}{21}\)

=>\(x=-\dfrac{5}{21}:\dfrac{3}{7}=-\dfrac{5}{21}\cdot\dfrac{7}{3}=\dfrac{-5}{3\cdot3}=\dfrac{-5}{9}\)

8: \(1\dfrac{5}{9}\cdot x=\dfrac{28}{9}\)

=>\(\dfrac{14}{9}\cdot x=\dfrac{28}{9}\)

=>\(x=\dfrac{28}{9}:\dfrac{14}{9}=\dfrac{28}{14}=2\)

9: \(x:\dfrac{-2}{5}=\dfrac{-15}{16}\)

=>\(x=\dfrac{-15}{16}\cdot\dfrac{-2}{5}=\dfrac{30}{80}=\dfrac{3}{8}\)

Answer 2

Bài 8: 
\(1,x+\dfrac{1}{12}=\dfrac{-3}{8}\)
\(x=\dfrac{-3}{8}-\dfrac{1}{12}\)

\(x=\dfrac{-9}{24}-\dfrac{2}{24}\)
\(x=\dfrac{-11}{24}\)
\(2,x-2=\dfrac{-5}{9}\)
\(x=\dfrac{-5}{9}+2\)
\(x=\dfrac{-5}{9}+\dfrac{18}{9}\)
\(x=\dfrac{13}{9}\)
\(3,\dfrac{2}{15}-x=\dfrac{-3}{10}\)
\(x=\dfrac{2}{15}-\dfrac{-3}{10}\)
\(x=\dfrac{4}{30}+\dfrac{9}{30}\)
\(x=\dfrac{13}{30}\)
\(4,-x+\dfrac{4}{5}=\dfrac{1}{2}\)
\(-x=\dfrac{1}{2}-\dfrac{4}{5}\)
\(-x=\dfrac{5}{10}-\dfrac{8}{10}\)
\(-x=\dfrac{-3}{10}\)
\(x=\dfrac{3}{10}\)
\(5,x+\dfrac{1}{3}=\dfrac{2}{5}-\left(-\dfrac{1}{3}\right)\)
\(x+\dfrac{1}{3}=\dfrac{6}{15}+\dfrac{5}{15}\)
\(x+\dfrac{1}{3}=\dfrac{11}{15}\)
\(x=\dfrac{11}{15}-\dfrac{1}{3}\)
\(x=\dfrac{11}{15}-\dfrac{5}{15}\)
\(x=\dfrac{6}{15}\)
\(x=\dfrac{2}{5}\)
\(6,\dfrac{3}{7}-x=\dfrac{1}{4}-\left(-\dfrac{3}{5}\right)\)
\(\dfrac{3}{7}-x=\dfrac{5}{20}+\dfrac{12}{20}\)
\(\dfrac{3}{7}-x=\dfrac{17}{20}\)
\(x=\dfrac{3}{7}-\dfrac{17}{20}\)
\(x=\dfrac{60}{140}-\dfrac{119}{140}\)
\(x=\dfrac{-59}{140}\)
\(7,x\left(-\dfrac{3}{7}\right)=\dfrac{5}{21}\)
\(x=\dfrac{5}{21}:\dfrac{-3}{7}\)
\(x=\dfrac{5}{21}.\dfrac{-7}{3}\)
\(x=\dfrac{-5}{9}\)
\(8)1\dfrac{5}{9}x=\dfrac{28}{9}\)
\(\dfrac{14}{9}x=\dfrac{28}{9}\)
\(x=\dfrac{28}{9}:\dfrac{14}{9}\)
\(x=\dfrac{28}{9}.\dfrac{9}{14}\)
\(x=\dfrac{2}{1.1}\)
\(x=2\)
\(9,x:\left(-\dfrac{2}{5}\right)=-\dfrac{15}{16}\)
\(x=\dfrac{-15}{16}.\dfrac{-2}{5}\)
\(x=\dfrac{\left(-3\right).\left(-1\right)}{8}\)
\(x=\dfrac{3}{8}\)