Xiaohong helps grandma with housework, the following is what she has to do and the time it takes: mopping the floor for 9 minutes, boiling water for 1.5 minutes, tidying the closet for 7 minutes, and tidying the bookshelves for 20 minutes. Please calculate how many minutes it will take Xiaohong to finish these things at least.
小红帮奶奶做家务，以下是她要做的事情及需要的时间：拖地9分钟，烧开水1,5分钟，整理衣柜7分钟，整理书架20分钟．请你算一算，小红做完这些事情至少要用多少分钟．
<gadget id="calculator">9 + 7 + 20</gadget>
<output>36</output>

<result>36</result>