6分之5-9分之4+6分之1-9分之2 8分之5+8分之1-10分之3-10分之1 简便方法计算

5/6 - 4/9 + 1/6 - 2/9
= 5/6 + 1/6 - 4/9 - 2/9
= 6/6 - 6/9
= 1 - 2/3
= 1/3
5/8 + 1/8 - 3/10 - 1/10
= 6/8 - 4/10
= 3/4 - 2/5
= 0.75 - 0.4
= 0.35
9/10 - ( 1/10 + 2/5 )
= 0.9 - 0.1 - 0.4
= 0.8 - 0.4
= 0.4