9: 3 = 36: 12, if the third item is subtracted by 12 and the left side remains unchanged, then how much is the fourth item subtracted.
9：3=36：12，如果第三项减去12，左侧不变，那么，第四项减去多少．
<gadget id="calculator">36 - 12</gadget>
<output>24</output>

<gadget id="calculator">24 / 36</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">12 * (2/3)</gadget>
<output>8</output>

<gadget id="calculator">12 - 8</gadget>
<output>4</output>

<result>4</result>