Add 10 to the latter term of 12:5, how much should be added to the former term to keep the ratio constant
把12：5的后项加10，要使比值不变，前项应加多少
<gadget id="calculator">5 + 10</gadget>
<output>15</output>

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

<gadget id="calculator">3 * 12</gadget>
<output>36</output>

<gadget id="calculator">36 - 12</gadget>
<output>24</output>

<result>24</result>