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

### Instruction:
 一家奶茶店昨天总共卖出了50杯奶茶。其中2/5是冬瓜口味，3/10是冲绳口味，剩下的是巧克力口味。昨天他们卖出了多少杯巧克力口味的奶茶？


### Response:
 冬瓜口味卖出了2/5 x 50 = <<2/5*50=20>>20杯。
冲绳口味卖出了3/10 x 50 = <<3/10*50=15>>15杯。
所以巧克力口味卖出了50 - 20 - 15 = <<50-20-15=15>>15杯。