How many {connector} are to/by {Universal Serial Bus} ?
What is the number of connectors in a USB
How many connectors are in a Universal Serial Bus?
SELECT ( COUNT ( ?o ) AS ?x ) { ?o property:connector resource:Universal_Serial_Bus }
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/P2935> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q42378 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P2935 wd:Q42378 }
10