CREATE TABLE table_18107 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Results" TEXT, "Candidates" TEXT)

Which district is Joe Moakley?
SELECT "District" FROM table_18107 WHERE "Incumbent" = 'Joe Moakley'
SELECT "District" FROM "table_18107" WHERE "Incumbent" = 'Joe Moakley'