[1-(1/2+1/3)×1/5]÷5/6
=(1-1/6×1/5)×6/5
=1×6/5-1/30×6/5
=30/25-1/25
=29/25
（2/3-12/7×7/24）÷7/3
=(2/3-1/2)×3/7
=2/3×3/7-1/2×3/7
=4/14-3/14
=1/14