Номер 1139

Обчисли:

1) 2/9 – (–1/18) + 1/2 = 2/9 + 1/18 + 1/2 = 4/18 + 1/18 + 9/18 = 14/18 = 7/9

2) –4/7 + 3/14 – 1/21 = –4/7 + 3/14 + (–1/21) = –24/42 + 9/42 + (–2/42) = –17/42

3) 1/6 – 3/8 – 5/12 + 2/3 = 1/6 + (–3/8) + (–5/12) + 2/3 = 4/24 + (–9/24) + (–10/24) + 16/24 = 1/24