user: Question: What is the biggest number for county population 18 years+?
Columns: ['College', '2007 Headcount', '2007-2008 credit hours', 'County population 18 yrs+', 'Penetration in terms of Enrollment per 1000 adults', 'In-county tuition per credit hour (fall 2009)']
Types: ['text', 'real', 'real', 'real', 'real', 'text']
Sample row: ['Atlantic', 6929.0, 143971.0, 282593.0, 25.0, '$93']
SQL:

assistant: SELECT MAX("County population 18 yrs+") FROM "Table";