Increase the former term of 3:4 by 6, to keep the ratio unchanged, how much should the latter term be increased.
把3：4的前项增加6，要使比值不变，后项应增加多少．
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

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

<result>8</result>