How many kills have 15 as the injured, with a year prior to 1987?
CREATE TABLE "europe" (
  "perpetrator" text,
  "date" text,
  "year" real,
  "location" text,
  "country" text,
  "killed" real,
  "injured" text
);
SELECT SUM("killed") FROM "europe" WHERE "injured"='15' AND "year"<1987;