8/9-3/8+1/9
=8/9+1/9-3/8
=1-3/8
=5/8
7/9-2/5-5/18
=7/9-5/18-2/5
=(14-5)/18-2/5
=1/2-2/5
=(5-2)/10
=3/10
5/12+3/4+2/3
=(5+3*3+2*4)/12
=22/12
=11/6
=1又6分之5
1/2+(2/3-1/4)
=1/2-1/4+2/3
=1/4+2/3
=(3+8)/12
=11/12
1-1/8-3/10
=(40-5-12)/40
=13/40
5/6-(1/2-1/3)
=5/6-1/2+1/3
=(5-3+2)/6
=4/6
=2/3