user: Question: How many listings under Melbourne has a distance at 15km?
Columns: ['Distance', 'Adelaide', 'Brisbane', 'Canberra', 'Melbourne', 'Perth', 'Sydney']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['0–5km', '$4.20', '$2.40', '$3.00', '$3.70', '$2.30', '$3.40']
SQL:

assistant: SELECT COUNT("Melbourne") FROM "Table" WHERE "Distance" = '15km';