In 2008, there were about 3.9 billion people in Asia, 400 million more than five times the total population of Europe. How many billion people are there in Europe?
2008年亚洲约有39亿人，比欧洲人口总数的5倍还多4亿人，欧洲大约有多少亿人．
<gadget id="calculator">39 - 4</gadget>
<output>35</output>

<gadget id="calculator">35 / 5</gadget>
<output>7</output>

<result>7</result>