(100 + 2) * 2 = 100 * 2 + 2 * 4 = 200 + 4 = 204, (200 - 2) * 15 = 200 * 15 – 2 * 15 = 3000 – 30 = 2970, 90 * 25 + 10 * 25 = (90 + 10) * 25 = 100 * 25 = 2500, 123 * 27 – 23 * 27 = (123 – 23) * 27 = 100 * 27 = 2700, 23 * 16 + 16 * 27 = 26 * (23 + 27) = 26 * 50 = 1300, 40 * 87 – 39 * 87 = 87 * (40 – 39) = 87 * 1 = 87.