A certain class counts the Chinese final exam results. The average score of the class is 85.13. After re-examination, Zhang Xiaomin’s score of 87 was mistaken for 78. After the re-examination, the average score is 85.31. How many people are there in this class?
某班统计语文期末考试成绩，班平均分85.13分，经复查张小敏的成绩87误为78分，重审后平均分为85.31分，问这个班有多少人？
<gadget id="calculator">87 - 78</gadget>
<output>9</output>

<gadget id="calculator">85.31 - 85.13</gadget>
<output>0.18</output>

<gadget id="calculator">9 / 0.18</gadget>
<output>50</output>

<result>50</result>