(2 5\9-120\21):1 8\49+1 8\9:6

1) 2 5/9 - 120/21 = 23/9 - 120/21 = → (общий знаменатель 63) → =     = 161/63 - 360/63 = - 199/632) - 199/63 : 1 8/49 = - 199/63 * 49/57 = - 1393/5133) 1 8/9 : 6 = 17/9 * 1/6 = 17/544) - 1393/13  + 17/54 = - 75222/702 + 221/702 = - 75001/702 =    = - 106 целых 589/702