9分之5+3分之2+9分之4
=5/9+4/9+2/3
=1+2/3
=1又2/3
6--7分之4--7分之3
=6-（4/7+3/70
=6-1
=5
7分之4+14分之1--2分之1
=8/14+1/14-7/14
=2/14
=1/7
8分之5--5分之2+8分之3
=5/8+3/8-2/5
=1-2/5
=3/5
4分之3+6分之1--3分之2
=9/12+2/12-8/12
=3/12
=1/4
5分之4-3分之2+5分之1--3分之1
=4/5+1/5-(2/3+1/3)
=1-1
=0