Ответ (RU):
a) 57a + 43a = 100a
При a = 321:
$$100 \cdot 321 = 32100$$
При a = 998:
$$100 \cdot 998 = 99800$$
б) 381p - 181p = 200p
При p = 59:
$$200 \cdot 59 = 11800$$
При p = 623:
$$200 \cdot 623 = 124600$$
в) 13a - 13b = 13(a - b)
При a = 407, b = 207:
$$13 \cdot (407 - 207) = 13 \cdot 200 = 2600$$