The average score of a certain class is 78.9, but when the score is counted in the middle, the score of a paper is misread, 96 is regarded as 69, and the average score after recalculation is 79.8. How many people are there in this class?
某班统计考试成绩，平均分是78.9，可是中间统计分数的时候把一份卷子的分数看错了，把96看成了69，重新计算的平均分是79.8，这个班有多少人？
<gadget id="calculator">96 - 69</gadget>
<output>27</output>

<gadget id="calculator">79.8 - 78.9</gadget>
<output>0.9</output>

<gadget id="calculator">27 / 0.9</gadget>
<output>30</output>

<result>30</result>