Номер 1381

1) 6a – 5a + 8a – 7a = 2a;

2) 9b + 12 – 8 – 4b = 5b + 4;

3) 5c + 4 – 2c – 3c = 4;

4) –7n + 8m – 13n – 3m = –20n + 5m.