А) 1 - k = 3/5 + 1/10;1 - k = (3 * 2 + 1 * 1)/10;1 - k = (6 + 1)/10;1 - k = 7/10;k = 1 - 7/10;k = 3/10;k = 0,3.Ответ: 3/10 или 0,3.Б) t + 1 = 4/9 + 2/3;t + 1 = (4 * 1 + 2 * 3)/9;t + 1 = (4 + 6)/9;t + 1 = 10/9;t = 10/9 - 1;t = 1/9.Ответ: 1/9.В) x + 2 3/8 = 5 1/4 - 1 3/8;х + 19/8 = 21/4 - 11/8;х = 21/4 - 11/8 - 19/8;х = (21 * 2 - 11 * 1 - 19 * 1)/8;х = (42 - 11 - 19)/8;х = 12/8;х = 3/2;х = 1 1/2;х = 1,5.Ответ: 1 1/2 или 1,5.