CREATE TABLE table_15681686_4 (rating VARCHAR, rank__week_ VARCHAR)

what is the rating where the rank is 48?
SELECT rating / SHARE(18 - 49) FROM table_15681686_4 WHERE rank__week_ = "48"
SELECT "rating" / NULLIF(SHARE(-31), 0) FROM "table_15681686_4" WHERE "48" = "rank__week_"