Ответ:

Пошаговое объяснение:

15-(x+ 3 6/7)=8 3/7. ​

15 - x - 3 6/7 = 8 3/7

11 1/7 - x = 8 3/7

x = 11 1/7 - 8 3/7

x = 10 8/7 - 8 3/7

x = 2 5/7

или так

15-(x+ 3 6/7)=8 3/7

x + 3 6/7 = 15 - 8 3/7

x + 3 6/7 = 6 4/7

x = 6 4/7 - 3 6/7

x = 5 11/7 - 3 6/7

x = 2 5/7