Bài 3:
a) \(x-\dfrac{6}{8}+\dfrac{1}{4}=3\)
\(\Rightarrow x-\dfrac{3}{4}+\dfrac{1}{4}=3\)
\(\Rightarrow x-\dfrac{1}{2}=3\)
\(\Rightarrow x=3+\dfrac{1}{2}\)
\(\Rightarrow x=\dfrac{7}{2}\)
b) \(x-7+\dfrac{4}{6}=\dfrac{-1}{5}\)
\(\Rightarrow x-7+\dfrac{2}{3}=\dfrac{-1}{5}\)
\(\Rightarrow x=\dfrac{-1}{5}-\dfrac{2}{3}+7\)
\(\Rightarrow x=-\dfrac{13}{15}+7\)
\(\Rightarrow x=\dfrac{92}{15}\)
Câu 4:
a: \(\dfrac{-1}{3}\cdot\dfrac{7}{24}:\dfrac{14}{36}\)
\(=\dfrac{-7}{72}\cdot\dfrac{36}{14}\)
\(=-\dfrac{7}{14}\cdot\dfrac{36}{72}=-\dfrac{1}{2}\cdot\dfrac{1}{2}=-\dfrac{1}{4}\)
b: \(\dfrac{5}{4}-\dfrac{1}{2}+\dfrac{-7}{8}\)
\(=\dfrac{10}{8}-\dfrac{4}{8}-\dfrac{7}{8}\)
\(=-\dfrac{1}{8}\)
Bài 4:
a) \(\dfrac{-1}{3}\cdot\dfrac{7}{24}:\dfrac{14}{36}\)
\(=\dfrac{-1}{3}\cdot\dfrac{7}{24}:\dfrac{7}{18}\)
\(=\dfrac{-1}{3}\cdot\dfrac{7}{24}\cdot\dfrac{18}{7}\)
\(=\dfrac{-1\cdot7\cdot18}{3\cdot24\cdot7}\)
\(=-\dfrac{1}{4}\)
b) \(\dfrac{5}{4}-\dfrac{1}{2}+\dfrac{-7}{8}\)
\(=\dfrac{5\cdot2}{4\cdot2}-\dfrac{1\cdot4}{2\cdot4}+\dfrac{-7}{8}\)
\(=\dfrac{10}{8}-\dfrac{4}{8}+\dfrac{-7}{8}\)
\(=\dfrac{10-4-7}{8}\)
\(=\dfrac{-1}{8}\)
