Объяснение:

№263

1)

3/7 + х = 13/14

х = 13/14 - 3/7

х = 13/14 - 6/14

х = 7/14

х = 1/2

2)

х - 5/8 = 11/12

х = 11/12 + 5/8

х = 22/24 + 15/24

х = 37/24

х = 1 13/24

№264

1)

7/36 + 1/5 + 5/36 = (7/36 + 5/36) + 1/5 = 12/36 + 1/5 = 1/3 + 1/5 = 5/15 + 3/15 = 8/15

2)

5/16 + 4/25 + 3/16 + 6/25 =

(5/16 + 3/16) + (4/25 + 6/25) = 8/16 + 10/25 =

1/2 + 2/5 = 5/10 + 4/10 = 9/10

3)

19/42 - (5/42 + 1/5) = 19/42 - 5/42 - 1/5 =

14/42 - 1/5 = 1/3 - 1/5 = 5/15 - 3/15 = 2/15

4)

(1/6 + 7/15) - 2/15 = 1/6 + 7/15 - 2/15 = 1/6 + 5/15 =

1/6 + 1/3 = 1/6 + 2/6 = 3/6 = 1/2

Verified answer

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