Найти значение выражения (х-2 3/5)+4 5/21=1 5/42

(х - 2 3/5) + 4 5/21 = 1 5/42;

х -  2 3/5 = 1 5/42 – 4 5/21;

х – 2 3/5 = 47/42 – 89/21;

х – 2 3/5 = 47/42 – (89 * 2) / (21 * 2);

х – 2 3/5 = 47/42 – 178/42;

х – 2 3/5 = -131/42;

х = -131/42 + 2 3/5;

х = -131/42 + 13/5;

х = -(131 * 5) / (42 * 5) + (13 * 42) / (5 * 42);

х = -655/210 + 546/210;

х = -109/210.

Проверка:

(-109/210 - 2 3/5) + 4 5/21 = 1 5/42;

(-109/210 – 13/5) + 4 5/21 = 1 5/42;

(-109/210 – 546/210) + 4 5/21 = 1 5/42;

-655/210 + 89/21 = 47/42;

-655/210 + 890/210 = 47/42;

235/210 = 47/42;

47/42 = 47/42. Решение выполнено верно.