In the ratio 3:12=6:24, if the latter term of the first ratio is increased by 6, then how much should the former term of the second ratio be to form a proportion.
在比例3：12=6：24中，如果将第一个比的后项增加6，那么要组成比例，第二个比的前项应多少．
<gadget id="calculator">3 * 24</gadget>
<output>72</output>

<gadget id="calculator">12 + 6</gadget>
<output>18</output>

<gadget id="calculator">72 / 18</gadget>
<output>4</output>

<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<result>2</result>