`3-4/5:1/3`
`=3-4/5xx3/1`
`=3-12/5`
`=15/5-12/5`
`=3/5`
`5/9xx2/7-3/7`
`=10/63-3/7`
`=10/63-27/63`
`=-17/63`
`12/8-3/4+3`
`=12/8-6/8+24/8`
`=30/8=15/4`
\(3-\dfrac{4}{7}:\dfrac{1}{3}\)
\(=3-\dfrac{4}{7}.\dfrac{3}{1}\)
\(=3-\dfrac{12}{5}\)
\(=\dfrac{15}{5}-\dfrac{12}{5}\)
\(=\dfrac{3}{5}\)
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\(\dfrac{5}{9}.\dfrac{2}{7}-\dfrac{3}{7}\)
\(=\dfrac{10}{63}-\dfrac{3}{7}\)
\(=\dfrac{10}{63}-\dfrac{27}{63}\)
\(=\dfrac{-17}{63}\)
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\(\dfrac{12}{8}-\dfrac{3}{4}+3\)
\(=\dfrac{12}{8}-\dfrac{6}{8}+\dfrac{24}{8}\)
\(=\dfrac{30}{8}=\dfrac{15}{4}\)
* Dấu . là dấu nhân