According to the fifth census, the population of Ningxia is about 6.6 million, which is less than the total population of Xi'an (3/25). What is the population of Xi'an?
第五次人口普查表明，宁夏全区人口约为660万，比西安市的人口总数少(3/25)．西安市的人口大约有多少万？
<result>770</result>