a, \(\dfrac{1}{2}-2\cdot y=\dfrac{9}{20}\\ \Leftrightarrow2y=\dfrac{1}{20}\\ \Leftrightarrow y=\dfrac{1}{40}\)
b, \(\dfrac{3}{5}:\dfrac{4}{3}:y=2+\dfrac{7}{10}\\ \Leftrightarrow\dfrac{9}{20y}=\dfrac{27}{10}\\ \Leftrightarrow y=\dfrac{1}{6}\)
c, \(y+\dfrac{3}{2}y-\dfrac{1}{2}y=\dfrac{1}{10}\\ \Leftrightarrow2y=\dfrac{1}{20}\\ \Leftrightarrow y=\dfrac{1}{40}\)

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