Tiantian Garment Factory has to process 1,200 sets of sportswear, and processed 20% of the total in the first 3 days. At this speed, how many days will it take for the rest?
天天制衣厂要加工1200套运动装，前3天加工了总数的20%，照这样的速度加工，剩下的还需要多少天？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) / 3</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / (1/15)</gadget>
<output>15</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<result>12</result>