There were five tests in this semester's mathematics class. Xiao Ming's score was 10 points more than the first time for the second time, 5 points less for the third time than the second time, 4 points more for the fourth time than the third time, and 4 points for the first 4 times. The average score is 85 points. If the fifth test is 13 points less than the fourth test, what is the average score of Xiao Ming's five tests in the whole semester?
本学期数学课进行了五次测验，小明的成绩第二次比第一次多10分，第三次比第二次少5分，第四次比第三次多4分，前4次的平均成绩是85分．如果第五次比第四次少13分，那么小明全学期五次测验的平均成绩是多少分？
<gadget id="calculator">89 - 10</gadget>
<output>79</output>

<gadget id="calculator">89 - 5</gadget>
<output>84</output>

<gadget id="calculator">84 + 4</gadget>
<output>88</output>

<gadget id="calculator">88 - 13</gadget>
<output>75</output>

<gadget id="calculator">79 + 89 + 84 + 88 + 75</gadget>
<output>415</output>

<gadget id="calculator">415 / 5</gadget>
<output>83</output>

<result>83</result>