Ответ:

1) 1/2 + 4/7 - 3/14 = 7/14 + 8/14 - 3/14 =  12/14 = 6/7

2) 1/5 - 2/15 + 1/30 = 6/30 - 4/30 + 1/30 = 3/30 = 1/10

3) 1/10 + 7/20 - 2/40 = 4/40 + 14/40 - 2/40 = 16/40 = 4/10 = 2/5

4) 17/20 - 3/10 - 11/60 = 51/60 - 18/60 - 11/60 = 22/60 = 11/30

5) 3/20 + 7/10 - 3/40 = 6/40 + 28/40 - 3/40 = 31/40

6) 9/40 + 3/4 - 19/20 = 9/40 + 30/40 - 38/40 = 1/40

Если честно, учи правила! Это основа! Ты потом не вывезешь!