1) 1,2 + 2/3 = 1.2/10 + 2/3 = 12/10 + 2/3 = 36/30 + 20/30 = 56/30 = 1.26/30 = 1.13/15
2) 2,25 - 1.1/6 = 2.25/100 - 7/6 = 225/100 - 7/6 = 45/20 - 7/6 = 9/4 - 7/6 = 27/12 - 14/12 = 13/12 = 1.1/12
3) 4/5 + 1,7 = 4/5 + 1.7/10 = 4/5 + 17/10 = 8/10 + 17/10 = 25/10 = 5/2 = 2.1/5