In 3:5, if 6 is added to the former term, how much should be added to the latter term to keep the ratio unchanged.
在3：5里，如果前项加上6，要使比值不变，后项应加多少．
<gadget id="calculator">3 + 6</gadget>
<output>9</output>

<gadget id="calculator">9 / 3</gadget>
<output>3</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<result>10</result>