72 : 2 = (60 + 12) : 2 = 60 : 2 + 12 : 2 = 30 + 6 = 36;
72 : 3 = (60 + 12) : 3 = 60 : 3 + 12 : 3 = 20 + 4 = 24;
18 * 4 = (10 + 8) * 4 = 10 * 4 + 8 * 4 = 40 + 32 = 72;
12 * 6 = (10 + 2) * 6 = 10 * 6 + 2 * 6 = 60 + 12 = 72;
9 * 8 = 72;
72 : 72 = 1;
72 : 1 = 72.