MySQL

SELECT ROUND(Long_w, 4)
FROM Station
WHERE  Lat_n < 137.2345
ORDER BY Lat_n DESC
LIMIT 1;

select round(long_w,4) from station where lat_n = (select max(lat_n) from station where lat_n < 137.2345

mySql:

one way:

select round(long_w,4) from station where lat_n = (select max(lat_n) from station where lat_n<137.2345)

other easy way but little bit different logic

select Round(LONG_W,4) from STATION where LAT_N<137.2345 order by LAT_N DESC LIMIT 1

WITH CTE AS ( SELECT LONG_W FROM STATION
WHERE LAT_N < 137.2345)

SELECT TOP 1 CAST(LONG_W AS NUMERIC (16,4)) FROM CTE WHERE LAT_N < 137.2345 ORDER BY LAT_N DESC;