The engineering team can repair a canal and work 5 hours and 18 days a day to complete it, if the work efficiency remains the same. Working 6 hours a day, how many days in advance can the task be completed?
工程队修一条水渠，每天工作5小时18天可以完成，如果工作效率不变．每天工作6小时，可以提前多少天完成任务？
<gadget id="calculator">5 * 18</gadget>
<output>90</output>

<gadget id="calculator">90 / 6</gadget>
<output>15</output>

<gadget id="calculator">18 - 15</gadget>
<output>3</output>

<result>3</result>