Verified answer

(9 - х) : 4 + 19 = 20

(9 - х) : 4 = 20 - 19

(9 - х) : 4 = 1

9 - х = 1 · 4

9 - х = 4

х = 9 - 4

х = 5

Проверка:

(9 - 5) : 4 + 19 = 20

4 : 4 + 19 = 20

1 + 19 = 20

20 = 20

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(3 + х) : 5 + 27 = 30

(3 + х) : 5 = 30 - 27

(3 + х) : 5 = 3

3 + х = 3 · 5

3 + х = 15

х = 15 - 3

х = 12

Проверка:

(3 + 12) : 5 + 27 = 30

15 : 5 + 27 = 30

3 + 27 = 30

30 = 30