user: Question: Which margin of defeats had points of 30?
Columns: ['Season', 'Driver', 'Team', 'Engine', 'Poles', 'Wins', 'Podiums', 'Points', 'Margin of defeat']
Types: ['real', 'text', 'text', 'text', 'real', 'real', 'real', 'text', 'text']
Sample row: [1950.0, 'Juan Manuel Fangio', 'Alfa Romeo', 'Alfa Romeo', 4.0, 3.0, 3.0, '27', '3']
SQL:

assistant: SELECT "Margin of defeat" FROM "Table" WHERE "Points" = '30';