This is a math homework problem about queuing. In the middle and lower grades of primary school, we have learned relevant knowledge. The focus of this topic is to understand the meaning of the word "zhong". According to the common sense of life, Xiao Ming is in the middle, which means there are as many people on both sides of Xiao Ming. According to the meaning, the formula is as follows: (15-1) ÷ 214 ÷ 27.