(1/2) of a is 20, b is (1/2) of 20, what is the difference between the two numbers
a的(1/2)是20，b是20的(1/2)，两数相差多少
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">20 / (1/2)</gadget>
<output>40</output>

<gadget id="calculator">20 * (1/2)</gadget>
<output>10</output>

<gadget id="calculator">40 - 10</gadget>
<output>30</output>

<result>30</result>