36 * 25 = (30 + 6) * 25 = 30 * 25 + 6 * 25 = 750 + 150 = 900,
или:
36 * 25 = 36 * (20 + 5) = 36 * 20 + 36 * 5 = 720 + 180 = 900,
125 * 12 = (100 + 20 + 5) * 12 = 100 * 12 + 20 * 12 + 5 * 12 =
= 1200 + 240 + 60 = 1500,
или:
125 * 12 = 125 * (10 + 12) = 125 * 10 + 125 * 2 = 1250 + 250 = 1500