Помогите пожалуйста, нужно полное решение

1) a = - 9       a = - 23

a = a + 2d

2d = a - a = - 23 - (- 9) = - 23 + 9 = - 14

d = - 7

a = a + 9d = - 9 + 9 * (- 7) = - 9 - 63 = - 72

Ответ : Д

2) a = - 2     a = 16

a = a + 6d

6d = a - a = 16 - (- 2) = 16 + 2 = 18

d = 3

a = a + 9d = - 2 + 9 * 3 = - 2 + 27 = 25

Ответ : A

3) a = - 5     a = - 29

a = a + 12d

12d = a - a = - 29 - (- 5) = - 29 + 5 = - 24

d = - 2

a = a + 9d = - 5 + 9 * (- 2) = - 5 - 18 = - 23

Ответ : Г

4) a = -1      a = 51

a = a + 13d

13d = a - a = 51 - (- 1) = 51 + 1 = 52

d = 4

a = a + 9d = - 1 + 9 * 4 = - 1 + 36 = 35

Ответ :  Б