21. Реши уравнения. x:9=11 x+75=2075 x・8=720 x-80=360 56:x=56 90-x=90

1. x : 9 = 11

   x = 11 ⋅ 9

   x = 99

   Проверка: 99:9 = 11

   11 = 11

2. x + 75 = 2075

   x = 2075 - 75

   x = 2000

   Проверка: 2000 + 75 = 2075

   2075 = 2075

3. x ⋅ 8 = 720

   x = 720 : 8

   x = 90

   Проверка: 90 ⋅ 8 = 720

   720 = 720

4. x - 80 = 360

   x = 360 + 80

   x = 440

   Проверка: 440 - 80 = 360

   360 = 360

5. 56 : x = 56

   x = 56 : 56

   x = 1

   Проверка: 56 : 1 = 56

   56 = 56

6. 90 - x = 90

   x = 90 - 90

   x = 0

   Проверка: 90 - 0 = 90

   90 = 90

Ответ: x = 99; x = 2000; x = 90; x = 440; x = 1; x = 0