Question: What is the average number for northgate which commenced its construction before 1951?
SQL: SELECT AVG("Number on map") FROM "2-156618-3" WHERE "Name" = 'northgate' AND "Construction commenced" < 1951.0;

Question: What is the lowest population for the neighborhood with the color blue that commenced its construction before 1987?
SQL: SELECT MIN("Population") FROM "2-156618-3" WHERE "Colour" = 'blue' AND "Construction commenced" < 1987.0;