45 : 3 = (30 + 15) : 3 = 30 : 3 + 15 : 3 = 10 + 5 = 15
56 : 4 = (40 + 16) : 4 = 40 : 4 + 16 : 4 = 10 + 4 = 14
38 : 2 = (40 - 2) : 2 = 40 : 2 - 2 : 2 = 20 - 1 = 19
72 : 6 = (60 + 12) : 6 = 60 : 6 + 12 : 6 = 10 + 2 = 12
51 : 3 = (60 - 9) : 3 = 60 : 3 - 9 : 3 = 20 - 3 = 17
78 : 6 = (60 + 18) : 6 = 60 : 6 + 18 : 6 = 10 + 3 = 13