Wang Ling has been reading a 290-page novel for 4 days, 20 pages a day, how many pages are left?
王玲看一本290页的小说，已经看了4天，每天看20页，还剩多少页？
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">290 - 80</gadget>
<output>210</output>

<result>210</result>