In the ratio 3:12=6:24, if we add 6 to the last term of the first ratio, what should be the former term of the second ratio, so that the ratio can be established.
在比例3：12=6：24中，如果将第一个比的后项加6，第二个比的前项应多少，比例才能成立．
<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>