Г: Вычислите: 3/7 + 13/35; 8/15 + 2/25; 1/7 − 1/8; 3/8 + 7/72; 13/20 − 3/8; 1/6 + 7/10; 1/6 − 1/12; 2/25 + 1/9; 3/4 − 31/42; 7/12 + 3/20; 19/21 − 5/6; 34/45 − 7/10; 4/21 + 9/14; 4/9 + 17/63; 11/24 − 7/16.

Приводим дроби к общему знаменателю, выполняем действие и сокращаем результат.

1. 3/7 + 13/35 = 15/35 + 13/35 = 4/5.
2. 8/15 + 2/25 = 40/75 + 6/75 = 46/75.
3. 1/7 − 1/8 = 1/56.
4. 3/8 + 7/72 = 27/72 + 7/72 = 17/36.
5. 13/20 − 3/8 = 26/40 − 15/40 = 11/40.
6. 1/6 + 7/10 = 5/30 + 21/30 = 13/15.
7. 1/6 − 1/12 = 1/12.
8. 2/25 + 1/9 = 18/225 + 25/225 = 43/225.
9. 3/4 − 31/42 = 63/84 − 62/84 = 1/84.
10. 7/12 + 3/20 = 35/60 + 9/60 = 11/15.
11. 19/21 − 5/6 = 38/42 − 35/42 = 1/14.
12. 34/45 − 7/10 = 68/90 − 63/90 = 1/18.
13. 4/21 + 9/14 = 8/42 + 27/42 = 5/6.
14. 4/9 + 17/63 = 28/63 + 17/63 = 5/7.
15. 11/24 − 7/16 = 22/48 − 21/48 = 1/48.