bài 2:
\(a,\dfrac{1}{3}:3x=\dfrac{20}{100}-\dfrac{2}{3}\\ \dfrac{1}{3}:3x=\dfrac{-7}{15}\\ 3x=\dfrac{1}{3}:\dfrac{-7}{15}\\ 3x=\dfrac{-5}{7}\\ x=\dfrac{-5}{7}:3\\ x=\dfrac{-5}{21}\\ b,\left(\dfrac{1}{2}-\dfrac{2}{3}\right)\cdot x=\dfrac{7}{12}\\\dfrac{-1}{6}x=\dfrac{7}{12}\\ x=\dfrac{7}{12}:\dfrac{-1}{6}\\ x=\dfrac{-7}{2}\\ c,\dfrac{1}{3}x=-1-\dfrac{2}{3}\\ \dfrac{1}{3}x=\dfrac{-1}{3}\\ x=\dfrac{-1}{3}:\dfrac{1}{3}\\ x=-1\\ d,7,5x:\left(9-\dfrac{139}{21}\right)=\dfrac{63}{25}\\ 7,5x:\dfrac{50}{21}=\dfrac{63}{25}\\ 7,5x=\dfrac{63}{25}\times\dfrac{50}{21}\\ 7,5x=6\\ x=0,8\)
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