Add 20 to the former term of 5:8, to keep the ratio constant, how much should be added to the latter term
把5：8的前项加上20，要使比值不变，后项应该加上多少
<gadget id="calculator">5 + 20</gadget>
<output>25</output>

<gadget id="calculator">25 / 5</gadget>
<output>5</output>

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

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

<result>32</result>