CREATE TABLE table_18438 ("District" CLOB, "Incumbent" CLOB, "Party" CLOB, "First elected" FLOAT, "Result" CLOB, "Candidates" CLOB)

When was James William Trimble first elected in the Arkansas 3 district?
SELECT MIN("First elected") FROM table_18438 WHERE "District" = 'Arkansas 3'
SELECT MIN("First elected") FROM "table_18438" WHERE "District" = 'Arkansas 3'