CREATE TABLE table_61529 ("Bow number" TEXT, "Ship name" TEXT, "Launched" TEXT, "Commissioned" TEXT, "Service" TEXT)

When did the ship commissioned in November 1975 with a bow number of ps-18 launch?
SELECT "Launched" FROM table_61529 WHERE "Commissioned" = 'november 1975' AND "Bow number" = 'ps-18'
SELECT "Launched" FROM "table_61529" WHERE "Bow number" = 'ps-18' AND "Commissioned" = 'november 1975'