\(\dfrac{18}{31}\times\dfrac{62}{9}\)
\(=\dfrac{18\times62}{31\times9}\)
\(=\dfrac{2\times2}{1}\)
\(=4\)
==============
\(\dfrac{35}{72}\times\dfrac{63}{20}\)
\(=\dfrac{35\times63}{72\times20}\)
\(=\dfrac{7\times7}{8\times4}\)
\(=\dfrac{49}{32}\)
===============
\(\dfrac{34}{65}:\dfrac{17}{15}\)
\(=\dfrac{34}{65}\times\dfrac{15}{17}\)
\(=\dfrac{34\times15}{65\times17}\)
\(=\dfrac{2\times3}{13\times1}\)
\(=\dfrac{6}{13}\)
===========
\(\dfrac{111}{64}:\dfrac{37}{40}\)
\(=\dfrac{111}{64}\times\dfrac{40}{37}\)
\(=\dfrac{111\times40}{64\times37}\)
\(=\dfrac{3\times5}{8\times1}\)
\(=\dfrac{15}{8}\)
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\(\dfrac{12}{19}\times\dfrac{41}{52}:\dfrac{82}{19}\)
\(=\dfrac{12}{19}\times\dfrac{41}{52}\times\dfrac{19}{82}\)
\(=\dfrac{12\times41\times19}{19\times52\times82}\)
\(=\dfrac{3\times1\times1}{1\times13\times2}\)
\(=\dfrac{3}{26}\)
