In 8:10, add 20 to the latter term, to keep the ratio unchanged, how much does the former term become.
在8：10中，后项加20，要使比值不变，那么前项变成多少．
<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">30 / 10</gadget>
<output>3</output>

<gadget id="calculator">8 * 3</gadget>
<output>24</output>

<result>24</result>