In 15:7, if 14 is added to the latter term of the ratio, how much should be added to the former term of the ratio to keep the ratio constant
在15：7中，如果比的后项加上14，要使比值不变，比的前项应加上多少
<gadget id="calculator">45 - 15</gadget>
<output>30</output>

<result>30</result>