The autumn grain output of a certain county last year was 39,000 tons, an increase of 30% over the previous year. What was the autumn grain output of the previous year?
某县去年秋粮产量为3.9万吨，比前年增长三成．前年秋粮产量是多少．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 + (3/10)</gadget>
<output>13/10 = around 1.3</output>

<gadget id="calculator">3.9 / (13/10)</gadget>
<output>3</output>

<result>3</result>