1/2+1/3=3/6+2/6=5/6
1/4+2/5=5/20+8/20=13/20
2/3+1/4=8/12+3/12=11/12
3/4+2/5=15/20+8/20=23/20=1 3/20
5/7-1/6=30/42-7/42=23/42
3/4-1/3=9/12-4/12=5/12
1/8+1/4=1/8+2/8=3/8
2/3-5/9=6/9-5/9=1/9
1/2-5/12=6/12-5/12=1/12
5/12-2/9=15/36-8/36=7/36
1/8+7/12=3/24+14/24=-17/24
3/4-1/6=9/12-2/12=7/12
5/9+3/4=20/36+27/36=47/36=1 11/36
23/40-3/8=23/40-15/40=8/40=1/5
9/35-3/28=36/140-15/140=21/140