The teacher issued several test papers, and calculated the student's personal score based on the average score of each test paper. If a student scored 97 points in the last test paper, his score can reach 90 points; if the student scored 73 points in the last test paper, his score is only 87 points. How many papers are there in this set?
老师出了若干份试卷，以每年学生各份试卷得分的平均数计算学生的个人成绩．如果某学生最后一份试卷得分为97分，他的成绩可达90分；如果该学生最后一份试卷得分为73分，他的成绩只有87分．这组试卷共有多少份．
<gadget id="calculator">97 - 73</gadget>
<output>24</output>

<gadget id="calculator">90 - 87</gadget>
<output>3</output>

<gadget id="calculator">24 / 3</gadget>
<output>8</output>

<result>8</result>