3/20-11/30=9/60-22/60=- 11/60
9/14+5/21=27/42+10/42=37/42
17/20+19/30=51/60+38/60=89/60=1 29/60
16/21-9/14=32/42-27/42=5/42
3/20-11/30=9/60-22/60=- 11/60
9/14+5/21=27/42+10/42=37/42
17/20+19/30=51/60+38/60=89/60=1 29/60
16/21-9/14=32/42-27/42=5/42