Выполни действие: 7/10+9/20 9/14-8/21 2,3-3/7

7/10 + 9/20 = (7 * 2 + 9 * 1)/20 = (14 + 9)/21 = 23/21 = 1 2/21;

Ответ: 1 2/21.

9/14 - 8/21 = (9 * 3 - 8 * 2)/42 = (27 - 16)/42 = 11/42;

Ответ: 11/42.

2,3 - 3/7 = 2 3/10 - 3/7 = 23/10 - 3/7 = (23 * 7 - 3 * 10)/70 = (161 - 30)/70 = 131/70 = 1 61/70.

Ответ: 1 61/70.