3分之1除以5分之6X10分之9
=1/3×(5/6×9/10)
=1/3×3/4
=1/4
42除以[14-(50-39)]
=42÷[14-11]
=42÷3
=14
2除以3分之2-3分之2除以2
=3-1/3
=2又2/3