user: Question: How many lengths of Line 3 are given?
Columns: ['Line', 'Terminals', 'Status', 'Length', 'Total number of stations', 'Operator']
Types: ['text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Line 1', 'Etxebarri / Plentzia', 'Complete', '31km', 29.0, 'Metro Bilbao S.A.']
SQL:

assistant: SELECT COUNT("Length") FROM "Table" WHERE "Line" = 'Line 3';