99 * 2 = (100 - 1) * 2 = 100 * 2 - 1 * 2 = 200 -2 = 198;
897 * 7 = (900 - 3) * 7 = 900 * 7 - 3 * 7 = 6300 - 21 = 6279;
403 * 6 = (400 + 3) * 6 = 400 * 6 + 3 * 6 = 2400 + 18 = 2418;
2 * (150 - 5) = 2 * (100 + 50 - 5) = 2 * 100 + 2 * 50 - 2 * 5 = 200 + 100 - 10 = 300 - 10 = 290.