1) 18 13/24 + 19/60 = 18 65/120 + 38/120 = 18 103/120 2) 8 13/20 - 18 103/120 = — (18 103/120 — 8 13/120) = -10 100/120 = -10 5/24 3) -10 5/24 + 10 5/24 = 0 Ответ: 0