(7 - 1 5/12) : 6,7 + (5,75 - 3 1/6) : 15,5 = 1 4/31
1) 7 - 1 5/12 = 6 12/12 - 1 5/12 = 5 7/12
2) 5,75 - 3 1/6 = 5 75/100 - 1 1/6 = 5 225/300 - 1 50/300 = 4 175/300 = 4 7/12
3) 5 7/12 : 6,7 = 67/12 : 67/10 = 67/12 * 10/67 = 10/12 = 5/6
4) 4 7/12 : 15,5 = 55/12 : 155/10 = 55/12 * 10/155 = 55/186
5) 5/6 + 55/186 = 155/186 + 55/186 = 210/186 = 1 24/186 = 1 4/31