в) 20: (x: 9) = 4 7-x-14 = 28 (63: y) 9 = 81 49 : y + 6 = 13 50-9-a = 23

Решим уравнения и сделаем проверку.

20 : (x : 9) = 4

x : 9 = 20 : 4

x : 9 = 5

x = 5 ⋅ 9

x = 45

Проверка:

20 : (45 : 9) = 4

20 : 5 = 4

4 = 4

Ответ: x = 45

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7 ⋅ x - 14 = 28

7 ⋅ x = 28 + 14

7 ⋅ x = 42

x = 42 : 7

x = 6

Проверка:

7 ⋅ 6 - 14 = 28

42 - 14 = 28

28 = 28

Ответ: x = 6

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(63 : y) ⋅ 9 = 81

63 : y = 81 : 9

63 : y = 9

y = 63 : 9

y = 7

Проверка:

(63 : 7) ⋅ 9 = 81

9 ⋅ 9 = 81

81 = 81

Ответ: y = 7

---

49 : y + 6 = 13

49 : y = 13 - 6

49 : y = 7

y = 49 : 7

y = 7

Проверка:

49 : 7 + 6 = 13

7 + 6 = 13

13 = 13

Ответ: y = 7

---

50 - 9 ⋅ a = 23

-9 ⋅ a = 23 - 50

-9 ⋅ a = -27

a = -27 : (-9)

a = 3

Проверка:

50 - 9 ⋅ 3 = 23

50 - 27 = 23

23 = 23

Ответ: a = 3