The average score of a test in a class is 70 points, among which (4/5) students pass, their average score is 80 points, what is the average score of the students who fail.
某班级一次考试的平均分数是70分，其中(4/5)的同学及格，他们的平均分是80分，不及格同学的平均分是多少分．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) * 80</gadget>
<output>64</output>

<gadget id="calculator">70 - 64</gadget>
<output>6</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">6 / (1/5)</gadget>
<output>30</output>

<result>30</result>