Xiao Ming has been reading a 180-page storybook for 4 days, 35 pages a day. How many pages are there yet?
小明看一本180页的故事书，已经看了4天，每天看35页．还有多少页没有看？
<gadget id="calculator">35 * 4</gadget>
<output>140</output>

<gadget id="calculator">180 - 140</gadget>
<output>40</output>

<result>40</result>