user: ### NOW ANSWER:
Question: What is the Average for Silver medals that have more than 17 Golds?
Columns: ['Rank', 'Nation', 'Gold', 'Silver', 'Bronze', 'Total']
Types: ['real', 'text', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'Brazil', 17.0, 18.0, 15.0, 50.0]
SQL:

assistant: SELECT AVG("Silver") FROM "Table" WHERE "Gold" > 17.0;