Columnar calculation: The grain output of a certain farm last year was 180 tons, but this year’s harvest is 20% less. How many tons is the grain output of this farm this year?
列式计算：某农场去年的粮食产量为180吨，今年少收二成，今年该农场的粮食产量是多少吨？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">180 * (4/5)</gadget>
<output>144</output>

<result>144</result>