CREATE TABLE table_18282 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

In which district is Robert W. Edgar the incumbent?
SELECT "District" FROM table_18282 WHERE "Incumbent" = 'Robert W. Edgar'
SELECT "District" FROM "table_18282" WHERE "Incumbent" = 'Robert W. Edgar'