−81/88 ⋅ (−6 + (−1 13/15) ⋅ (−1 19/21))

Шаг 1: Преобразуем смешанные числа в неправильные дроби.

−1 13/15 = −(15+13)/15 = −28/15

−1 19/21 = −(21+19)/21 = −40/21

Шаг 2: Выполним умножение дробей внутри скобок.

(−28/15) ⋅ (−40/21) = (28 ⋅ 40) / (15 ⋅ 21) = (4 ⋅ 7 ⋅ 8 ⋅ 5) / (3 ⋅ 5 ⋅ 3 ⋅ 7) = (4 ⋅ 8) / (3 ⋅ 3) = 32/9

Шаг 3: Выполним сложение внутри скобок.

−6 + 32/9 = −54/9 + 32/9 = −22/9

Шаг 4: Выполним умножение.

−81/88 ⋅ (−22/9) = (81 ⋅ 22) / (88 ⋅ 9) = (9 ⋅ 9 ⋅ 2 ⋅ 11) / (8 ⋅ 11 ⋅ 9) = (9 ⋅ 2) / 8 = 18/8 = 9/4