A survey was conducted on the breakfast situation of students. There are 391 students who eat breakfast every day, accounting for 85% of the total number of students in the school. How many people cannot guarantee to eat breakfast every day?
对学生早餐情况进行调查，每天吃早餐的有391人，占全校总数的85%，不能保证每天吃早餐的有多少人？
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">391 / (17/20)</gadget>
<output>460</output>

<gadget id="calculator">460 - 391</gadget>
<output>69</output>

<result>69</result>