user: Question: What was the average rank for south africa when they had more than 8 silver medals?
Columns: ['Rank', 'Nation', 'Gold', 'Silver', 'Bronze', 'Total']
Types: ['real', 'text', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'United States', 50.0, 41.0, 32.0, 123.0]
SQL:

assistant: SELECT AVG("Rank") FROM "Table" WHERE "Nation" = 'south africa' AND "Silver" > 8.0;