2: Add 9 to the latter term of 3, how many times should the former term be increased to keep the ratio constant.
2：3的后项加上9，要使比值不变，前项应增加多少倍．
<gadget id="calculator">3 + 9</gadget>
<output>12</output>

<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<result>3</result>