Xiaoming, Xiaohong and Xiaoying visit Teacher Wang regularly. Xiaoming visits Teacher Wang every 6 days, Xiaohong visits every 8 days, and Xiaoying visits Teacher Wang every 9 days. How many days do they visit Teacher Wang at the same time?
小明、小红和小英三人定期向王老师，小明每6天去一次，小红每8天去一次，小英每9天去一次，他们每多少天会同时看王老师？
<gadget id="calculator">2 * 2 * 2 * 3 * 3</gadget>
<output>72</output>

<result>72</result>