CREATE TABLE table_18311 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

What district did Dave Treen serve?
SELECT "District" FROM table_18311 WHERE "Incumbent" = 'Dave Treen'
SELECT "District" FROM "table_18311" WHERE "Incumbent" = 'Dave Treen'