Divide 102 by 2 times of x, the quotient is 0.4, find x?
102除x的2倍，商是0.4，求x？
<gadget id="calculator">0.4 * 102</gadget>
<output>40.8</output>

<gadget id="calculator">40.8 / 2</gadget>
<output>20.4</output>

<result>20.4</result>