0,8 + 3/7 = 8/10 + 3/7 = 4/5 + 3/7 = (28+15)/35 = 43/35 = 1 8/35
3 1/3 - 2,5 = 10/3 - 2 1/2 = 10/3 - 5/2 = (20-15)/6 = 5/6
4,9 + 1 1/9 = 4 9/10 + 1 1/9 = 49/10 + 10/9 = (441+100)/90 = 541/90 = 6 1/90
26 1/11 - 5,7 =287/11 - 5 7/10 = 287/11 - 57/10 =(2870-627)/110 = 2243/110 = 20 43/110
40,8 + 15 2/3 = 40 4/5 + 15 2/3 = 204/5 + 47/3 = (612+235)/15 = 847/15 = 56 7/15