Mr. Wang counted the scores of a mathematics test. The average score of 42 students who took the test was 83.5. During the review, it was found that one student's score of 81 was miscalculated as 18. What is the correct average score of this test?
王老师统计一次数学考试成绩，参加考试的42名同学的平均成绩为83.5分，在复查中发现把一名同学的81分错算成了18分，这次考试正确的平均成绩是多少分？
<gadget id="calculator">42 * 83.5</gadget>
<output>3_507</output>

<gadget id="calculator">81 - 18</gadget>
<output>63</output>

<gadget id="calculator">3_507 + 63</gadget>
<output>3_570</output>

<gadget id="calculator">3_570 / 42</gadget>
<output>85</output>

<result>85</result>