1-6/19=19/19-6/19= 13/19
5-4/11=4,11/11-4/11= 4,7/11
18,4/9-9= 9,4/9
18-3,7/15= 17,15/15-3,7/15= 14, 8/15
2,3/4 - 1,7/12 = 2,9/12-1,7/12= 1,2/12 = 1,1/6