(4/5-k)-1/3=1/6-1/10

(4/5 - k) - 1/3 = 1/6 - 1/10;
(4/5 - k) - 1/3 = (1 * 5)/(6 * 5) - (1 * 3)/(10 * 3);
(4/5 - k) - 1/3 = 5/30 - 3/30;
(4/5 - k) - 1/3 = 2/30;
(4/5 - k) = 2/30 + 1/3;
(4/5 - k) = 2/30 + (1 * 10)/(3 * 10);
(4/5 - k) = 2/30 + 10/30;
(4/5 - k) = 12/30;
к = 4/5 - 12/30;
к = (4 * 6)/(5 * 6) - 12/30;
к = 24/30 - 12/30;
к = 12/30;
к = 2/5.
Проверка:
(4/5 - 2/5) - 1/3 = 1/6 -1/10;
2/5 - 1/3 = (1 * 5)/(6 * 5) - (1 * 3)/(10 * 3);
(2 * 3)/(5 * 3) - (1 * 5)/(3 * 5) = 5/30 - 3/30;
6/15 - 5/15 = 2/30;
1/15 = 2/30;
1/15 = 1/15. Решение выполнено правильно.