This year our school will be on holiday from February 7th, and school will start on March 9th. How many days are there in this holiday?
今年我们学校从2月7日开始放假，3月9日开学，这个假期共有多少天．
<gadget id="calculator">28 - 7</gadget>
<output>21</output>

<gadget id="calculator">21 + 1 + 8</gadget>
<output>30</output>

<result>30</result>