SELECT COUNT("Races") FROM table_3298 WHERE "Points" = '15'
How many series awarded 15 points?
CREATE TABLE table_3298 (
    "Season" real,
    "Series" text,
    "Team" text,
    "Races" real,
    "Wins" real,
    "Poles" real,
    "F/Laps" real,
    "Podiums" real,
    "Points" text,
    "Position" text
)