CREATE TABLE table_203_839 (id DECIMAL, "station" TEXT, "type" TEXT, "latitude" TEXT, "longitude" TEXT, "el.  ( m ) " DECIMAL, "opened" DECIMAL, "closed" DECIMAL, "coordinates" TEXT)

elevation difference in mount montezuma , chile and mount brukkaros , namibia
SELECT (SELECT "el. (m)" FROM table_203_839 WHERE "station" = 'mount montezuma, chile') - (SELECT "el. (m)" FROM table_203_839 WHERE "station" = 'mount brukkaros, namibia')
SELECT (SELECT "el. (m)" FROM "table_203_839" WHERE "station" = 'mount montezuma, chile') - (SELECT "el. (m)" FROM "table_203_839" WHERE "station" = 'mount brukkaros, namibia')