Bài 5:
a) Ta có: \(x+\dfrac{1}{12}=\dfrac{-3}{8}\)
nên \(x=\dfrac{-3}{8}-\dfrac{1}{12}=\dfrac{-9}{24}-\dfrac{2}{24}=\dfrac{-11}{24}\)
b) Ta có: \(x-2=\dfrac{-5}{9}\)
nên \(x=\dfrac{-5}{9}+2=\dfrac{-5}{9}+\dfrac{18}{9}=\dfrac{13}{9}\)
c) Ta có: \(\dfrac{2}{15}-x=\dfrac{-3}{10}\)
nên \(x=\dfrac{2}{15}+\dfrac{3}{10}=\dfrac{4}{30}+\dfrac{9}{30}=\dfrac{13}{30}\)
d) Ta có: \(\dfrac{4}{5}-x=\dfrac{1}{2}\)
nên \(x=\dfrac{4}{5}-\dfrac{1}{2}=\dfrac{8}{10}-\dfrac{5}{10}=\dfrac{3}{10}\)
Bài 7:
a) Ta có: \(x+\dfrac{1}{3}=\dfrac{2}{5}-\left(-\dfrac{1}{3}\right)\)
\(\Leftrightarrow x+\dfrac{1}{3}=\dfrac{2}{5}+\dfrac{1}{3}\)
\(\Leftrightarrow x=\dfrac{2}{5}\)
b) Ta có: \(\dfrac{3}{7}-x=\dfrac{1}{4}-\left(-\dfrac{3}{5}\right)\)
\(\Leftrightarrow\dfrac{3}{7}-x=\dfrac{1}{4}+\dfrac{3}{5}=\dfrac{17}{20}\)
hay \(x=\dfrac{3}{7}-\dfrac{17}{20}=\dfrac{-59}{140}\)
