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

### Instruction:
 一个农民有51头奶牛。农民增加了5头新奶牛到他的牛群中，然后卖掉了四分之一的牛。农民还剩下多少头奶牛？


### Response:
 农民的牛群有51+5 = <<51+5=56>>56头奶牛。
农民卖掉了牛群的56/4 = <<56/4=14>>14头奶牛。
农民现在还剩下56-14 = <<56-14=42>>42头奶牛。