Show locations for stations.
select location from station
Show locations for stations with at least 15 platforms.
select location from station where number_of_platforms >= 15
Among those, which locations also have stations with more than 25 total passengers?
select location from station where number_of_platforms >= 15 and total_passengers > 25
Show distinct locations of them.
select distinct location from station where number_of_platforms >= 15 and total_passengers > 25