9/10 + 3/10 = 12/10= 1 2/10
7/9 - 5/7 = 2/63
5/6 + 1/9 = 17/18
17/18 - 11/12 = 17*2-11*3 /36 = 1/36
1 2/9 + 3 1/3 = (1+3)+ 4/9 = 4 4/9
5 3/4 -2 = 3 3/4
4 - 1 7/9 = 2 2/9
4 1/3 - 1 1/2 = 2 5/6
3/5:11/15=3*15 / 5*11 = 45/55 = 9/11
27/40 : 18/35=27*35/40*18=945/720=1 45/144
1 : 3/7 = 2 1/3
8/27 *36 -8*36/27= 32/3 = 10 2/3