1 /2+4/7-3/14=(7+8-3)/14=12/14=6/7
1/5-2/15+1/30=(6-4+1)/30=3/30=1/10
1/10+7/20-2/40=(4+14-2)/40=16/40=2/5
17/20-3/10-11/60=(51-18-11)/60=22/60=11/30
9/40+3/4-19/20=(9+30-38)/40=1/40
1)79/80-(3/16+39/80)=
79/80-((15+39)/80)=79/80-54/80=25/80=5/16
2)2/45+(41/45-7/9)=
2/45+6/45=8/45
3)7/15-(2/15+17/5)=
7/15-53/15=-46/15
4)3/16+(15/16-5/8)=3/16+5/16=8/16=1/2