CREATE TABLE table_204_520 (id DECIMAL, "outcome" TEXT, "no." DECIMAL, "date" DECIMAL, "championship" TEXT, "surface" TEXT, "opponent" TEXT, "score" TEXT)

what surface was used before carpet ?
SELECT "surface" FROM table_204_520 WHERE id = (SELECT id FROM table_204_520 WHERE "surface" = 'carpet') - 1
SELECT "surface" FROM "table_204_520" WHERE "id" = (SELECT "id" FROM "table_204_520" WHERE "surface" = 'carpet') - 1