user: Question: what is the average gold when rank is total and silver is more than 20?
Columns: ['Rank', 'Nation', 'Gold', 'Silver', 'Bronze', 'Total']
Types: ['text', 'text', 'real', 'real', 'real', 'real']
Sample row: ['1', 'China (CHN)', 9.0, 2.0, 3.0, 14.0]
SQL:

assistant: SELECT AVG("Gold") FROM "Table" WHERE "Rank" = 'total' AND "Silver" > 20.0;