CREATE TABLE table_76176 ("Tie no" TEXT, "Home team" TEXT, "Score" TEXT, "Away team" TEXT, "Date" TEXT)

What was the tie number when peterborough united was the away team?
SELECT "Tie no" FROM table_76176 WHERE "Away team" = 'peterborough united'
SELECT "Tie no" FROM "table_76176" WHERE "Away team" = 'peterborough united'