user: Question:  how many countries sampled with year of publication being 2007 and ranking l.a. (2) being 7th
Columns: ['Index (Year)', 'Author / Editor / Source', 'Year of publication', 'Countries sampled', 'World Ranking (1)', 'Ranking L.A. (2)']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Environmental Performance (2008)', 'Yale University', '2008', 149.0, '32nd', '5th']
SQL:

assistant: SELECT SUM("Countries sampled") FROM "Table" WHERE "Year of publication" = '2007' AND "Ranking L.A. (2)" = '7th';