(1-2/5÷4/5)÷5/4
=1÷5/4-2/5÷4/5÷5/4
=4/5-[2/5÷(4/5×5/4)]
=4/5-(2/5-÷1)
=4/5-2/5
=2/5
希望能帮到你
(1-2/5÷4/5)÷5/4
=1÷5/4-2/5÷4/5÷5/4
=4/5-[2/5÷(4/5×5/4)]
=4/5-(2/5-÷1)
=4/5-2/5
=2/5
（1－1/2÷4/5）×5/6
=(1-1/2*5/4)*5/6
=(1-2/5)*5/6
=3/5*5/6
=1/2
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