Xiao Ming's average score in the previous math tests was 84. This time, he needs to score 100 points to raise his average score to 86. How many tests is this? Use two methods of solving equations and calculating formulas.
小明前几次数学测验的平均成绩是84分，这一次要考100分，才能把平均成绩提高到86分，这是第几次测验？使用解方程和算式两种方法．
<gadget id="calculator">100 - 84</gadget>
<output>16</output>

<gadget id="calculator">86 - 84</gadget>
<output>2</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>