23 * 3 = (20 + 3) * 3 = 20 * 3 + 3 * 3 = 60 + 9 = 69;
24 * 3 = (20 + 4) * 3 = 20 * 3 + 4 * 3 = 60 + 12 = 72;
25 * 3 = (20 + 5) * 3 = 20 * 3 + 5 * 3 = 60 + 15 = 75;
26 * 3 = (20 + 6) * 3 = 20 * 3 + 6 * 3 = 60 + 18 = 78;

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