Add 12 to the former term of 3:8, to keep the size of the fraction unchanged, how much should the latter term be increased
把3：8的前项加上12，要使分数的大小不变，后项应增加多少
<gadget id="calculator">3 + 12</gadget>
<output>15</output>

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

<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<gadget id="calculator">40 - 8</gadget>
<output>32</output>

<result>32</result>