1) 8,5 - 1/3 = 85/10 - 1/3 = 17/2 - 1/3 = 51/6 - 2/6 = 49/6 = 8 1/6
2) 4 1/9 + 1,8 = 4 1/9 + 18/10 = 4 1/9 + 9/5 = 4 5/45 + 81/45 = 4 86/45 = 5 41/45
3) 1/9 * 0,12 = 1/9 * 12/100 = 1/9 * 6/50 = 6/450 = 1/75
4) 6/7 : 0,6 = 6/7 : 6/10 = 6/7 * 10/6 = 10/7 = 1 3/7