The difference between the two piles of goods is 20 tons. After they have been shipped out by 10%, how many tons is the difference between the two piles of goods?
两堆货物相差20吨，它们各运出10%后，这时两堆货物相差多少吨
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 * (9/10)</gadget>
<output>90</output>

<gadget id="calculator">100 - 20</gadget>
<output>80</output>

<gadget id="calculator">80 * (9/10)</gadget>
<output>72</output>

<gadget id="calculator">90 - 72</gadget>
<output>18</output>

<result>18</result>