SELECT "Home (1st leg)" FROM table_12740 WHERE "Aggregate" = '3-1'
What was the first leg home that had a total aggregate of 3-1?
CREATE TABLE table_12740 (
    "Home (1st leg)" text,
    "Home (2nd leg)" text,
    "1st Leg" text,
    "2nd leg" text,
    "Aggregate" text
)