The former term of the ratio is 3, and the latter term is 4. If 9 is added to the former term of the ratio, how much should the latter term be multiplied to keep the ratio constant.
比的前项是3，后项是4，如果比的前项加上9，要使比值不变，比的后项应乘以多少．
<gadget id="calculator">9 + 3</gadget>
<output>12</output>

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

<result>4</result>