The math score of a certain class was calculated with an average score of 87.13. After re-examination, it was found that Wu Jiang's score of 98 was mistaken for 89. After calculation, the average score was 87.31. How many students are there in this class?
某班统计数学成绩，得平均分为87.13，经复查，发现将吴江的98分误作89分，再计算，平均分为87.31求这个班有学生多少人．
<gadget id="calculator">98 - 89</gadget>
<output>9</output>

<gadget id="calculator">87.31 - 87.13</gadget>
<output>0.18</output>

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

<result>50</result>