Xiaoqing's average score in the previous math tests this semester was 80 points, but the latest test score was 100 points, and the average score increased to 85 points. So how many times is this test?
小青这学期前几次数学测验的平均分是80分，最近这次测验得100分，平均分提高到85分．那么这次测验是第多少次．
<gadget id="calculator">100 - 80</gadget>
<output>20</output>

<gadget id="calculator">85 - 80</gadget>
<output>5</output>

<gadget id="calculator">20 / 5</gadget>
<output>4</output>

<result>4</result>