A story book has 400 pages, Xiao Liang has read 280 pages, how many pages does Xiao Liang not read?
一本故事书有400页，小亮看了280页，小亮还剩多少页没有看？
<gadget id="calculator">400 - 280</gadget>
<output>120</output>

<result>120</result>