How many {place served by transport hub} are to/by {Rome} ?
Is Rome served through a number of transport centers?
Rome is served by how many  transport hubs?
SELECT ( COUNT ( ?z ) AS ?y ) { ?z property:place_served_by_transport_hub resource:Rome }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P931> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q220 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P931 wd:Q220 }
6