user: Question: In the District Tennessee 7 what is the number of first elected?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Tennessee 2', 'Howard Baker, Sr.', 'Republican', 1950.0, 'Re-elected', 'Howard Baker, Sr. (R) 68.9% Boyd W. Cox (D) 31.1%']
SQL:

assistant: SELECT "First elected" FROM "Table" WHERE "District" = 'Tennessee 7';