Below is an instruction that describes a task. Write a response that appropriately completes the request in French. Please answer in French.

### Instruction:
 Sam has 18 cows.  5 more than half the cows are black.  How many cows are not black?


### Response:
 Soit n le nombre de vaches qui ne sont pas noires. Nous savons que n + 18 = 18 + 5/2 = 21 vaches, donc n = 21 - 18 = <<21-18=3>>3.