bonsoir

12 : - 3 = - 4

7 + ( - 4 ) =  3

- 2  - ( - 18 ) = - 2 + 18 = 16

- 9 : - 9 = 1  

Explications étape par étape:

a. 12/-3 = 4/-1 = -4

b. 7 + (-8/2) = 7 - 4 = 3

c. (4/-2 ) - (-3×6) = -2 - (-18) = -2 + 18 = 16

d. -9/(-5-4) = -9/-9 = 1