Xiaoli borrowed a 150-page fairy tale. She reads 20 pages a day. How many pages are left after a week?
小丽借了一本150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">150 - 140</gadget>
<output>10</output>

<result>10</result>