Найдите значение выражения 1 2/21 – 8/35.

Источник: Ященко ОГЭ 2025 (36 вар.)

Решение:

1 2/21 – 8/35 = 1 ⋅ 21 + 2 / 21 – 8 / 35 = 23/21 – 8/35 = 23/ 3 ⋅ 7 – 8 / 5 ⋅ 7 = 23 ⋅ 5 – 8 ⋅ 3 / 3 ⋅ 5 ⋅ 7 = 115 – 24 / 3 ⋅ 5 ⋅ 7 = 91 / 3 ⋅ 5 ⋅ 7 = 13 / 3 ⋅ 5 ⋅ 1 = 13/15

Ответ: 13