Obviously borrowed a 160-page fairy tale. She reads 20 pages a day, how many pages are left after a week?
明明借了一本160页的童话故事．她每天看20页，一个星期后还剩多少页没有看？
<gadget id="calculator">20 * 7</gadget>
<output>140</output>

<gadget id="calculator">160 - 140</gadget>
<output>20</output>

<result>20</result>