4 11/15+2 7/20 = 4 44/60 + 2 21/60 = 7 1/12
4 11/15 - 2 7/20 = 4 44/60 - 2 21/60 = 2 23/60
4 11/15+2 7/20=6+11/15+7/20=6+44/60+21/60=6+65/60=6+13/12=7 1/12
4 11/15+2 7/20 = 4 44/60 + 2 21/60 = 7 1/12
4 11/15 - 2 7/20 = 4 44/60 - 2 21/60 = 2 23/60
4 11/15+2 7/20=6+11/15+7/20=6+44/60+21/60=6+65/60=6+13/12=7 1/12