Решим примеры на умножение:
1) 99 * 4 = (100 - 1) * 4 = 400 - 4 = 396
2) 39 * 7 = (40 - 1) * 7 = 280 - 7 = 273
3) 199 * 5 = (200 - 1) * 5 = 1000 - 5 = 995
4) 69 * 6 = (70 - 1) * 6 = 420 - 6 = 414
5) 49 * 4 = (50 - 1) * 4 = 200 - 4 = 196
6) 79 * 3 = (80 - 1) * 3 = 240 - 3 = 237