7分之6-9分之7+7分之8
=6/7+8/7-7/9
=2-7/9
=11/9
18分之17-10分之3-5分之1
=17/18-(3/10+1/5)
=17/18-1/2
=8/18
=4/9
9分之5-12分之5+9分之4
=5/9+4/9-5/12
=1-5/12
=7/12
12分之5-(12分之5-3分之1)
=5/12-5/12+1/3
=0+1/3
=1/3
3分之2+10分之7-10分之7+3分之2
=2/3+2/3+(7/10-7/10)
=4/3
2-7分之3-7分之4
=2-(3/7+4/7)
=2-1
=1
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