Xiaohong has 280 stamps, which is 100 more than Xiaohua's (2/5). How many stamps does Xiaohua have?
小红有280张邮票，比小华邮票的(2/5)多100张，小华有多少张邮票．
<gadget id="calculator">280 - 100</gadget>
<output>180</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">180 / (2/5)</gadget>
<output>450</output>

<result>450</result>