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

### Instruction:
 蓝娜计划在义卖会上卖出20个松饼。她早上卖了12个松饼。下午她又卖了4个。蓝娜还需要卖多少个松饼才能达到她的目标？


### Response:
 蓝娜已经卖出了12个松饼，还需要卖出20 - 12 = 8个松饼才能在义卖会结束前达到目标。
然后她下午又卖出了4个松饼，剩下的需要卖出的松饼数量为8 - 4 = <<8-4=4>>4个。