Add 14 to the former term of 7:4, how much should be added to the latter term to keep the ratio constant
将7：4的前项加上14，要使比值不变，后项应该加上多少
<gadget id="calculator">7 + 14</gadget>
<output>21</output>

<gadget id="calculator">21 / 7</gadget>
<output>3</output>

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

<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<result>8</result>