467 Решите уравнение: a) (x + 2) + x = 9; б) x + (7 + x) = 11; в) х + 2x 5 = 40; г) х + (x + 4) + x = 16; д) (х + 5) + (x + 6) = 21; e) 2(x8) = 20.

1. a) (x + 2) + x = 9

   x + 2 + x = 9

   2x = 9 - 2

   2x = 7

   x = 7 / 2 = 3,5

2. б) x + (7 + x) = 11

   x + 7 + x = 11

   2x = 11 - 7

   2x = 4

   x = 4 / 2 = 2

3. в) х + 2x - 5 = 40

   3x = 40 + 5

   3x = 45

   x = 45 / 3 = 15

4. г) х + (x + 4) + x = 16

   x + x + 4 + x = 16

   3x = 16 - 4

   3x = 12

   x = 12 / 3 = 4

5. д) (х + 5) + (x + 6) = 21

   x + 5 + x + 6 = 21

   2x + 11 = 21

   2x = 21 - 11

   2x = 10

   x = 10 / 2 = 5

6. e) 2(x - 8) = 20

   2x - 16 = 20

   2x = 20 + 16

   2x = 36

   x = 36 / 2 = 18

Ответ: а) 3,5; б) 2; в) 15; г) 4; д) 5; е) 18.