The road construction team wants to build a 180-kilometer-long road. Originally, it built 6 kilometers a day. After 15 days, it speeded up to 7.5 kilometers a day. How many days will it take to finish the road?
筑路队要修一条长180千米的路，原来每天修6千米，修了15天以后加快速度，每天修7.5千米，修完这条路还要多少天？
<gadget id="calculator">6 * 15</gadget>
<output>90</output>

<gadget id="calculator">180 - 90</gadget>
<output>90</output>

<gadget id="calculator">90 / 7.5</gadget>
<output>12</output>

<result>12</result>