How many kills have 15 as the injured, with a year prior to 1987?
CREATE TABLE table_59529 (
    "Perpetrator" text,
    "Date" text,
    "Year" real,
    "Location" text,
    "Country" text,
    "Killed" real,
    "Injured" text
)
SELECT SUM("Killed") FROM table_59529 WHERE "Injured" = '15' AND "Year" < '1987'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: How many kills have 15 as the injured, with a year prior to 1987? ### Input: CREATE TABLE table_59529 (
    "Perpetrator" text,
    "Date" text,
    "Year" real,
    "Location" text,
    "Country" text,
    "Killed" real,
    "Injured" text
) ### Response: SELECT SUM("Killed") FROM table_59529 WHERE "Injured" = '15' AND "Year" < '1987'