Table: black_point
Columns: name
population_2011
population_2006
change
land_area_km
population_density_per_km

Question: What is the population density (per km) that has -6.7 as the change (%)?
SQL: SELECT "population_density_per_km" FROM black_point WHERE "change" = '-6.7'

Question: What population density (per km) that has 84 as the population (2006)?
SQL: SELECT "population_density_per_km" FROM black_point WHERE "population_2006" = '84'