7:
a: =\(\dfrac{1\cdot1\cdot1}{3\cdot6\cdot9}=\dfrac{1}{162}\)
b: \(=\dfrac{1}{18}\cdot9=\dfrac{1}{2}\)
c \(=\dfrac{1}{3}\cdot6\cdot\dfrac{1}{9}=\dfrac{2}{9}\)
\(6/\)
\(a,\dfrac{2}{5}\times\dfrac{3}{8}+\dfrac{3}{4}=\dfrac{2\times3}{5\times8}+\dfrac{3}{4}=\dfrac{6}{40}+\dfrac{3}{4}=\dfrac{3}{20}+\dfrac{3}{4}=\dfrac{3}{20}+\dfrac{15}{20}=\dfrac{18}{20}=\dfrac{9}{10}\)
\(b,\dfrac{2}{5}+\dfrac{3}{8}\times\dfrac{3}{4}=\dfrac{2}{5}+\dfrac{3\times3}{8\times4}=\dfrac{2}{5}+\dfrac{9}{32}=\dfrac{109}{160}\)
\(c,\dfrac{3}{4}:\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{3}{4}\times5-\dfrac{1}{3}=\dfrac{3\times5}{4}-\dfrac{1}{3}=\dfrac{15}{4}-\dfrac{1}{3}=\dfrac{41}{12}\)
\(7/\)
\(a,\dfrac{1}{3}\times\dfrac{1}{6}\times\dfrac{1}{9}=\dfrac{1\times1\times1}{3\times6\times9}=\dfrac{1}{162}\)
\(b,\dfrac{1}{3}\times\dfrac{1}{6}:\dfrac{1}{9}=\dfrac{1}{3}\times\dfrac{1}{6}\times9=\dfrac{9}{3\times6}=\dfrac{9}{18}=\dfrac{1}{2}\)
\(c,\dfrac{1}{3}:\dfrac{1}{6}\times\dfrac{1}{9}=\dfrac{1}{3}\times6\times\dfrac{1}{9}=\dfrac{6}{3\times9}=\dfrac{6}{27}=\dfrac{2}{9}\)
