CREATE TABLE table_29557 ("Season" TEXT, "Points per Game" TEXT, "Total Yards per Game" TEXT, "Rushing Yards per Game" TEXT, "Passing Yards per Game" TEXT, "Sacks" TEXT, "Interceptions" TEXT)

How many seasons have a sacks of 39?
SELECT COUNT("Season") FROM table_29557 WHERE "Sacks" = '39'
SELECT COUNT("Season") FROM "table_29557" WHERE "Sacks" = '39'