320.
a) \(\dfrac{25}{42}-\dfrac{20}{63}\)
\(=\dfrac{75}{126}-\dfrac{40}{126}\)
\(=\dfrac{35}{126}\)
\(=\dfrac{5}{18}\)
b) \(\dfrac{9}{50}-\dfrac{13}{75}-\dfrac{1}{6}\)
\(=\dfrac{27}{150}-\dfrac{26}{150}-\dfrac{25}{150}\)
\(=\dfrac{-24}{150}\)
\(=\dfrac{-4}{25}\)
c) \(\dfrac{2}{15}-\dfrac{2}{65}-\dfrac{4}{39}\)
\(=\dfrac{26}{195}-\dfrac{6}{195}-\dfrac{20}{195}\)
\(=0\)
321.
a) \(x+\dfrac{7}{2}=\dfrac{17}{18}-\dfrac{1}{9}\)
\(x+\dfrac{7}{12}=\dfrac{17}{18}-\dfrac{2}{18}\)
\(x+\dfrac{7}{12}=\dfrac{15}{18}\)
\(x+\dfrac{7}{12}=\dfrac{5}{6}\)
\(x=\dfrac{5}{6}-\dfrac{7}{12}\)
\(x=\dfrac{10}{12}-\dfrac{7}{12}\)
\(x=\dfrac{3}{12}\)
\(x=\dfrac{1}{4}\)
b) \(\dfrac{29}{30}-\left(\dfrac{13}{23}-x\right)=\dfrac{7}{69}\)
\(\dfrac{13}{23}-x=\dfrac{29}{30}-\dfrac{7}{69}\)
\(\dfrac{13}{23}-x=\dfrac{667}{690}-\dfrac{70}{690}\)
\(\dfrac{13}{23}-x=\dfrac{597}{690}\)
\(\dfrac{13}{23}-x=\dfrac{199}{230}\)
\(x=\dfrac{13}{23}-\dfrac{199}{230}\)
\(x=\dfrac{130}{230}-\dfrac{199}{230}\)
\(x=\dfrac{-69}{230}\)
\(x=\dfrac{-3}{10}\)
\(320.\)
\(a.\dfrac{25}{42}-\dfrac{20}{63}=\dfrac{75}{126}-\dfrac{40}{126}=\dfrac{35}{126}=\dfrac{5}{18}\)
\(b.\dfrac{9}{50}-\dfrac{13}{75}-\dfrac{1}{6}=\dfrac{27}{150}-\dfrac{26}{150}-\dfrac{25}{150}=\dfrac{-24}{150}=\dfrac{-4}{25}\)
\(c.\dfrac{2}{15}-\dfrac{2}{65}-\dfrac{4}{39}=\dfrac{26}{195}-\dfrac{6}{195}-\dfrac{20}{195}=\dfrac{0}{195}\)
Câu c hơi lạ :D
mình cảm ơn các bạn ạ
