2/17+7/17 7/16-5/16 2/25+9/25 12/13-3/13

1) 2/17 + 7/17 = (2 + 7) / 17 = 9/17;

2) 7/16 - 5/16 = (7 - 5) / 16 = 2/16 = 2 / (2 * 8) = 1/8;

3) 2/25 + 9/25 = (2 + 9) / 25 = 11/25;

4) 12/13 - 3/13 = (12 - 3) / 13 = 9/13.

Решим подобные примеры, для закрепления материала:

1) 3/14 + 5/14 = (3 + 5) / 14 = 8/14 = (2 * 4) / (2 * 7) = 4/7;

2) 5/18 + 5/18 = (5 + 5) / 18 = 10/18 = (2 * 5) / (2 * 9) = 5/9;

3) 7/10 + 3/10 = (7 + 3) / 10 = 10/10 = 1;

4) 9/22 + 3/22 = (9 + 3) / 22 = 12/22 = (2 * 6) / (2 * 11) = 6/11;

5) 3/26 + 7/26 + 5/26 = (3 + 7) / 26 + 5/26 = 10/26 + 5/26 = (10 + 5) / 26 = 15/26.