A wire is 800m long, and 45% of the total length is used up. How much m is left?
一根电线长800m，用去了全长的45%，还剩多少m．
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">800 * (9/20)</gadget>
<output>360</output>

<gadget id="calculator">800 - 360</gadget>
<output>440</output>

<result>440</result>