user: Question: How many sales had a peak position of 1 and a certification of 6x platinum?
Columns: ['Rank', 'Artist', 'Album', 'Peak position', 'Sales', 'Certification']
Types: ['real', 'text', 'text', 'real', 'real', 'text']
Sample row: [1.0, 'Lady Gaga', 'The Fame', 1.0, 560000.0, '7x Platinum']
SQL:

assistant: SELECT COUNT("Sales") FROM "Table" WHERE "Peak position" = 1.0 AND "Certification" = '6x platinum';