1) 3/5-1/4+1/3=41/60
3/5-1/4=12/20-5/20=7/20
7/20+1/3=21/60+20/60=41/60
2) (2/3+1/9)-13/18=1/18
2/3+1/9=6/9+1/9=7/9
7/9-13/18=14/18-13/18=1/18
3) 3/4-1/2+7/8=1. 1/8
3/4-1/2=3/4-2/4=1/4
1/4+7/8=2/8+7/8=9/8=1 1/8
4) 5/6-2/3+1/4=5/12
5/6-2/3=5/6-4/6=1/6
1/6+1/4=2/12+3/12=5/12
5) 1/3-(1/9+1/6)=1/18
1/9+1/6=2/18+3/18=5/18
1/3-5/18=6/18-5/18=1/18