а) 1/3 + 1/6 + 1/18 = 6/18 + 3/18 + 1/18 = 10/18 = 5/9
б) 1/2 + 1/5 + 3/7 = 21/42 + 8/42 + 18/42 = 47/42 = 1 5/42
в) 1/2 + 1/3 + 3/5 = 30/60 + 20/60 + 36/60 = 86/60 = 43/30