Dongfeng Motor Group originally planned to manufacture a batch of high-end export cars, 18 cars per day, and it would take 30 days to complete. How many days in advance can it be done if 2 more cars are made every day?
东风汽车集团原计划制造一批高级出口轿车，每天制造18辆，要30天完成．如果每天多制造2辆，可以提前多少天完成？
<gadget id="calculator">18 + 2</gadget>
<output>20</output>

<gadget id="calculator">30 / 20</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">18 * (3/2)</gadget>
<output>27</output>

<gadget id="calculator">30 - 27</gadget>
<output>3</output>

<result>3</result>