Regulations: a*b=(1/4)ab-a, then 4*(8*9)=how much.
规定：a*b=(1/4)ab-a，则4*(8*9)=多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) * 8 * 9</gadget>
<output>18</output>

<gadget id="calculator">18 - 8</gadget>
<output>10</output>

<gadget id="calculator">(1/4) * 4 * 10</gadget>
<output>10</output>

<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<result>6</result>