16 целых 2/5- 4 целых 3/7= 16 (2•7)/(5•7) - 4 (3•5)/(7•5)= 16 14/35- 4 15/35= 15 (35•1+14)/35- 4 15/35= 15 49/35- 4 15/35= 11 34/35. 19 целых 5/12 - 8 целых 17/18= 19 (5•3)/(12•3) - 8 (17•2)/(18•2)= 19 15/36- 8 34/36= 18 (36•1+15)/36 - 8 34/36= 18 51/36 - 8 34/36= 10 17/36