Xingxing Garment Factory wanted to produce a batch of 1,200 performance costumes for the closing ceremony of the Asian Games. The original plan was to make 100 pieces per day. After 4 days, the work efficiency was improved, and 60 more pieces were done every day than the original plan. How many days earlier than originally planned?
星星服装厂要为亚运会闭幕式赶制一批表演服装1200件，原计划每天做100件．4天以后，提高了工作效率，每天比原计划多做60件．这样比原计划提前几天完成？
<gadget id="calculator">1_200 / 100</gadget>
<output>12</output>

<gadget id="calculator">100 * 4</gadget>
<output>400</output>

<gadget id="calculator">1_200 - 400</gadget>
<output>800</output>

<gadget id="calculator">100 + 60</gadget>
<output>160</output>

<gadget id="calculator">800 / 160</gadget>
<output>5</output>

<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">12 - 9</gadget>
<output>3</output>

<result>3</result>