Номер 251

1) 102 · 13 – (100 + 2) · 13 = 1800 + 26 = 1326;

2) 997 · 15 – (1000 – 3) · 15 = 15 000 – 45 = 14955;

3) 71 · 80 = 71 · (100 – 20) = 7100 – 1420 = 5680;

4) 600 · 88 = 600 · (100 – 12) = 60 000 – 7200 = 52 800.