2/9+3/7
59/60+39/40
3 /5-1/7
11/80-11/90
2/5×3/7
5×2/11
4/5÷3/7
3/11:9 ?

2/9+3/7= 14/63+27/63=41/63
59/60+39/40=118/120+117/120=235/120
3/5-1/7=21/35-5/35=16/35
11/80-11/90=880/7200-990/7200=-110/7200=55/3600=1/720
2/5*3/7=6/35
5*2/11=5/1*2/11=10/11
4/5:3/7=4/5*7/3=28/15
3/11:9=3/11*1/9=3/11