CREATE TABLE table_203_193 (id DECIMAL, "ship name" TEXT, "in service" DECIMAL, "project number" TEXT, "type" TEXT, "class" TEXT, "comments" TEXT)

what is the difference in years in service of the taymyr and the arktika ?
SELECT (SELECT "in service" FROM table_203_193 WHERE "ship name" = 'taymyr') - (SELECT "in service" FROM table_203_193 WHERE "ship name" = 'arktika')
SELECT (SELECT "in service" FROM "table_203_193" WHERE "ship name" = 'taymyr') - (SELECT "in service" FROM "table_203_193" WHERE "ship name" = 'arktika')