По действиям...
1)2:3(1/5)=2*5/16=5/8
2)3(1/4)-2/3=13/4-2/3=39/12-8/12=31/12
3)2(5/18)-17/36=41/18-17/36=82/36-17/36=46/36=23/18
4)31/12:3= 31/12*1/3=31/36
5)23/18:65/18=23/18*18/65=23/65
6)5/8-31/36=45/72-62/72=-17/72
7)-17/72-23/65=-1105/4680-1656/4680=2761/4680