Ответ:

1) числитель

1/4 * 4 = 1

1 3/4 : 1 = 1 3/4 = 7/4

1 3/4 * 2/5 = 7/4 *2/5 = 7/10

7/10 + 7/4 = 14/20 + 35/20 = 49/20

49/20 * 1 5/7 = 49/20 * 12/7 = 21/5

2) знаменатель

425/1000 - 13/40 = 425/1000 - 325/1000= 100/1000 = 1/10

1/10 : 2/5 = 1/10 * 5/2 = 1/4

1/4 : 2 1/2 = 1/4 : 5/2 = 1/4 * 2/5 =  1/10

3) 21/5 : 1/10 = 21/5 * 10 = 42