（1）5又5/6+4.5-10又1/3
=35/6+9/2-31/3
=35/6+27/6-62/6
=62/6-62/6
=0
(2)[20%+(2-1.4)]÷3/20
=(0.2+2-1.4)*20/3
=0.8*20/3
=16/3
(3)2/5÷[(2又1/2-1又1/3)÷1又1/6]
=2/5÷[(5/2÷4/3)÷7/6]
=2/5÷(7/6÷7/6)
=2/5÷1
=2/5