Xiaoyue reads a 63-page storybook. She reads 7 pages a day for 6 days. How many pages are left in the storybook?
小月看一本63页的故事书，她每天看7页，看了6天，这本故事书还剩多少页没看完？
<gadget id="calculator">7 * 6</gadget>
<output>42</output>

<gadget id="calculator">63 - 42</gadget>
<output>21</output>

<result>21</result>